Yes it is common and acceptable for the pianist to hug/kiss(on the cheek) the conductor.
Lol what if they made out on the stage!
I know that for encores, you bow, walk off, come back on, bow, play, bow walk off, and keep doing the same thing. It doesn't really sound that bad but if you're in the royal Albert hall and you have to walk up those looooong stairs, it's tiring lol.