Is this position legal?

Wow, we have some interesting positions.

Wow, we have some interesting positions.

legal...

This one?

This one is legal. Knight came and cuted off everything

is this one?

or this one?

this one is illegal, but why?

Black king is checked, so it must have been white's move previously. But the only square the bishop could have come from is d6, which would have meant black was checked the previous move too, without escaping = illegal.

yes!

is it?

The position above is illegal because the only way either side could get more than one pawns on a file is if the pawn made a capture, and each side has all of its pieces.

#159 illegal, black needs at least 15 captures.

#160 legal, 8 pieces missing and 8 captures needed for the pawns to cross.

Is this legal ? And what about if b5 is moved to b6 ?

no.....two dark squared bishops....and no. 

That position is legal but with pawn on b6 it is inpossible because the white's  bishop has no way to go to a1

because b6-pawn prevents it's route b8-a7-d4-a1 

I don't agree. 

Here's my contribution!