I have been using the P3 cap on my 2.5 for a good year now with no problems...No.
Button top batteries only with the 2.5.
You should not use the high performance bottom cap with the 2.5.
The board on the 2.5 is glued in place.
The new bottom cap will put too much pressure on the board and may break it loose, same goes for the stock P3 bottom cap, this directly from ProVape.