How to stop the hitting?

It's also important to teach him positive responses to those big feelings when he's in a calm state.  Some breathing exercises or ways to take a moment to self sooth so that he is able to think about how his actions might affect outcomes.  It will be a process that takes time, and you will need to remind him of those techniques sometimes when he's starting to feel stressed, but he will start to get into the habit and use them himself more often.

You could even work on the techniques together and then ask him to remind you of them if he thinks you need help too.  This helps him to understand that everyone gets angry, but it's the reactions that are a problem.

lol my sister does that, always shouting stuff but her kid was too young to understand and just laughed at her anyway and continued. its only when they got older when she could take their playstation away or their android phone away that they began to listen to her as obviously kids hooked on those gadgets dont want them to go and will do anything to keep them even if it means being good.

This is true. I do explain things to him when he’s a calm and he seems to take it in better 

Yes he does. They have a very close bond and adore each other but my partner is autistic too and so he struggles terribly with our son’s meltdowns and doesn’t handle it the right way I feel. I prefer the more calm approach but his approach is to just shout ‘No’ constantly

this is probably one of those things best left to the father, does he have one by any chance?

Talk to him about hitting when he is calm when his brain is more accepting of new information. Children can't process things when they're that upset.  

Think about how hard it is for you as an adult to manage your emotions, and then think about how much harder it must be for a child who is not fully physically developed or have your level of experience.  

I haven’t got any advice but just wanted to say I’m in the exact same boat as you. Since staring nursery in September after turning 3 his behaviour has been terrible and he has suddenly became incredibly cheeky, hitting, kicking etc. when he first started he wasn’t really doing much of this so don’t know if it’s copying other children. He’s no angel though! A few months ago he went through an awful stage where he wasn’t getting his way and therefore would just lash out at anything and anyone in sight. This was usually me as I’m off on maternity leave. He’d come straight up to me and slap me across the face, hit me with no care in world. I’d sit in a state in tears just having to let him attack me as I didn’t have any energy left to fight or tell him no.. not that that he listens when I tell him off. 
I used to feel sick and get myself in a state going to pick him up from nursery because of the fear of what they were going to say he’d done to other kids. He’s not as bad now but it’s the whole turning up feeling like the terrible parent with everyone judging you because your son is the ‘naughty child’ 

We are a nice ‘normal’ family and the thought of people looking down on you and your child or the fear of my son being left out or not invited to a child’s party because he’s naughty is heartbreaking. 

Anyway, just wanted to say I’m the exact same boat as you with an almost 4) year old and struggling daily with his behaviour. I don’t want to take him places including now to see my sister as I’m starting to sense her getting annoyed at his behaviour and I can’t be bothered with constant ‘NO!’ at him. Like you, I try to take the calm approach as much as I can as I feel this works better but when he’s constantly being told no you can’t do this and you can’t do that it winds me up. 

I just don't know if this will pass either or if this is an autistic trait. I know kids hit but the stage he went through was extreme 

As soon as I got close to a meltdown at that age I was forced to take a 5 to fifteen minute quiet sit on the end of the bed in a quiet room, and I think I once earned a slap on the legs when I resisted the process. (Obviously this was real hard work for the supervising adult because it only works if you make sure the kid actually does sit still, but they MADE me do it) It taught me the required degree of self control t not be a completely horrible and unmanageable child.

When my child bit me on day when I was not doing what she wanted, I applied physical retaliation without even thinking about it, but in a restrained manner, which surprised both of us, but she never did it, or anything like it again. I was mostly able to use humour and total honesty to train my kid. On the few occasions she got the better of me as kids can, rather than losing my rag, or being a martyr as many parents do, I simply told her, that she's being bad at a time when I am busy and "if she does not stop it, I'll have to punish her. I don't know what I'll do, I'm too busy to think about it, but it'll come up with something and it won;t be good. Do you want that?" 

When eventually she really wanted to know what I'd do, and I did actually have time to tell her, I told her of a ficticious place where bad children were sent to be made into sausages, which of course she found highly enjoyable, teasing the details out of me, and completely forgot whatever the original point of contention was...

A four year old kid KNOWS you have the power, the key is to make them want you to use it for them rather than against them. Hitting them outside of an instinctive response to unprovoked violence is not a useful punishment, my childhood taught me. In fact if you have to actually punish your child to change their behaviour I believe you are losing, I used to negotiate everything that I could rather than impose rules. If they figure out the rules themselves, even if it's through decoding your humour and sarcasm they seem to take 'em onboard deeper than if you just impose them.

MY kid turned out way better than i did, so some of it must have worked..

Elle1994 said:

because he didn't do anything wrong. That's why I tell him that it is OK for his brother to play with the toys,

that's right. But neither understands it. They're too young yet. Try setting a time limit. E.g. ask older ''Would it be OK if your younger could get that toy to play with in 10min?''

I prefered to play solo as well, until I was over 5y.o. It's difficult to communicate with others, about common endeavour. Then I started with my younger sisters, we managed to build some kind of understanding, so we could discuss doing things together.

Elle1994 said:

He does speak,

about anything he can loook at objectively, I mean without being part of it, 

When he is asked about situation he was in, he will be confused to describe it, emotions gets in a way.

Thank you for replying!! My 4 year old was lining up his cars when his brother took the monkey so his attention was only on the monkey when his brother started to play with it, its a hard line because his little brother is curious and wants to play and i don't think its right that i take toys off my toddler because he didn't do anything wrong. That's why I tell him that it is OK for his brother to play with the toys, I do try the distraction technique but it rarely is successful.

We went to a group the other week and my 4 year old was fascinated with a toy microwave. He wouldn't let anyone get a look in, he was playing with it for an hour (open door, close door, let it spin for 3 seconds, open door, close door, repeat etc) again I told him that other children can play and maybe we can go to the ball pit instead, he then jabbed a little girl in her forehead because she put a toy in the microwave. The mum ended up coming up to me and saying my child was a bully etc.

He does speak, his speech is good, he speaks in third person and has an insane memory! Hes very clever and is like a sponge haha. But he does struggle with basic communication, he couldn't tell you how old he is but could recite a whole episode hes watched (or something i told him a year ago!) 

Hi

It looks to me he struggles with autistic intertia, which is changing plans, activities, anything without enough time or/and info to process it.

''It's OK, your brother can play with your toy'' to him might mean you approve those interruptions.

Slapping might be letting you know it's happening, since he doesn't speak yet, or does he?