UKC

Yes or no? Why?

Maybe

Sometimes, but not usually. HTH

Yes. I'm an international diamond thief. 

If you're Pinocchio, probably not a good idea

Yes for improving skin regrowth (counter intuitively)

I don't know, why can skin care possibly be important for climbers?  I remember back when I was in my slab climbing prime, cranking with one finger on a pebble, sure of the send, on the crux move of Satin E3 6b.

Have you ever ripped your finger tip off? 

I scraped my finger tip across a metre of gritstone as I fell.  Luckily a nurse in my parents' parish who was a family friend patched me up really well and told me the best thing was to leave my skin on the wound, whether it was dead skin or the good stuff.

I did not use the opportunity to commit any sort of crimes with one finger - they would never have been able to trace me, as I had no finger prints, Mwahahaaa!

Someone would have fingered you eventually.

Ooo-er missus!

Yes, for improving skin regrowth, yes for healing splits, yes for repairing flappers and tears evenly, and yes for reducing the chance of flappers.

If you have dry skin then it's a good way to both prevent and help heal recurring splits by sanding down to the full depth of the split, so the skin heals in one even layer.

If your skin gets calloused or forms a thick hard layer it's much more prone to tearing/flappers as the hard layer detaches from the soft skin beneath. Sanding down the hard skin gets rid of the 'hard-on-soft' combo that causes the issue.

I use a whiteboard marker wrapped in sandpaper to get into the finger creases several times a week.