Am 27,I dated a guy for 4yrs,later found out he was cheating on me we broke up for 8months,he's back says he's changed &wants to marry me but he hasn't engage me.my mum dislikes him.is he for real?

Kick to the curb. Move on. He is not the one 4 you. If you question his motives, that should tell you your answer.

Try a long (one year) engagement.

It is hard to say if he has changed or not, giving him a chance is up to you.
Mom's often know or have a feel for things.