white to play and win

White must play d8 and promote to a knight. After that use the knight and the pawns to stop the bishop from giving checkmate. For example Ba8 Nc6 Bxc6 e8=Q Bxe8 g8=Q 1-0

after d8=n Bd5 ?

Ilamparthi   you   must   play d8=N  Bd5  then g8=Q 1-0                                 

d8=N Bd5 g8=Q Ke3 and it's a draw.

The threat is King moves and mate. White has to play accurately to win.

3.Be4 and there's one more move white has to find.

promote e pawn to rook. Classic underpromotion puzzle with three underpromotions

I'd never seen it before, neat puzzle with 3 underpromotions 

I hadn't seen it earlier too. When I said classic I didn't mean famous, I meant wonderful (maybe bad choice of word)
The first one with knight was obvious. Then tried queen with g pawn and there was a stalemate. Hence found the bishop. Then again tried queen with e pawn and another stalemate! Hence, rook. Trial and error on a physical board with real pieces is how I got it

nice underpromotion tactic