We are blasting our garage footprint in a couple weeks and am looking for best advice on footers and slab. 

Location: SW Colorado – 9300 ft elevation. 260 annual inches of snowfall. 
Soil: solid granite. No topsoil at all. 
Garage will be ICF and the back will be on piers. 

Do my footings need to be blasted into rock or can they be pinned on top? How thick do they need to be?

How thick should the slab be?

Can the piers be poured anon top and pinned as well?

Do I need to worry about water getting between rock and concrete, freezing, and causing movement?

I attached a picture showing elevation. Ground slopes down from right to left. 
Thank you!