does riley come back after he left? and does buffy go out with angel again? and why

Yes Riley comes back to see Buffy to have her help to defeat a demon that he has been searching for from Central American. Also along with him was his wife that happening surprise Buffy.

Buffy doesn't got back with Angel. He went back to LA to defeat Demons their in his own world. See the relationship with Buffy/Angel is that they fight evil thats there destiny not fallen in love. But Buffy goes with out Spike just using him for sexual violence because Buffy was feeling punished and disoriented from being back from her grave.

Does Riley come back after he left?
Yes he comes back because they hear of a huge evil presence in Sunnydale.
Does Buffy go out with Angel again?
In the Buffy series angal comes back to help Buffy and be there for her. She does go to LA to help Angel and let him know a few things to keep him in the loop. But one time in an Angel episode they do get together because he turns human and they can finally have the love and love making they don't have to worry about him going all Angelus. But he goes to the powers that be to reverse his humanity because Buffy needs help to continue their fight against evil!! That was a great episode!!!