What slips, laps and rolls, yet is stuck to the same spot for its lifetime?

I clean your face or cover your lap, maybe in a pinch even wipe your crap.

I'm at the tip of a tongue, but not part of it, yo. I'm what boys seek, but can't find it, ya know? I've been called button, pearl, hat, and bean. For a bear in SF, I'll never be seen. Push too hard and you will regret, but you tread lightly... bet.

Mick is one. Skip it for fun. In the UK, a bunch add up to a ton To kill two birds, use it, don't bother with a gun.

I’ve got four legs but never wear shoes, I chase my own tail like it’s breaking news. I bark at the mailman like he’s a spy - What am I, with a wag and a slobbery hi?