Would you say he has autism/adhd?

my stepson is 9 years old. he’s always been hard to deal with as long as I’ve known him since a baby. he has tantrums and meltdowns which can last ages. Half of the time he doesn’t understand why you’ve said “don’t do that”. he won’t stop and just carry on doing it. Basically won’t listen to simple instructions. he won’t understand why he can’t do something or why someone else can’t play with him at that time because they’re doing something or why he shouldn’t kick his sister because it’s wrong and will upset her. He will still go ahead and kick her. Just now we were at his mums house ready to leave and he just jumped in the car and we were there for 10mins asking/begging him to get out. We finally told him he needs to go change his clothes before he comes out so he went in the house and realised he can’t come with us and had a huge meltdown went hysterical and didn’t stop crying for over 30mins. Started hitting his brother and sister. This can’t be normal behaviour. 😭 He also doesn’t seem to understand empathy. His mum is on the waiting list to see a specialist but it’s taking forever and we just don’t know how to deal with this behaviour it’s like we need professional help 😭