assuming that adam pushed kaito off the building and then regenerated once he fell. who do u think will win, when hiro goes back to that day to stop his fathers death

I think hiro is goning to freeze up and miss saving his father but then he will kill adam afterward puting a end to all that immortality s*#t with a knife to the heart

Since Adam meets Peter after those events, I would bet that's not what happens.

The initial Adam/Peter meeting happens BEFORE Kaito's Death... regardless, just because something happened in the show does not mean it cannot be reversed.