[Routine help] How resilient is retinol once it's been absorbed by the skin?

Beauty Tips For Body Care
I'd like to know if it breaks down from sunlight easily a while after it's been applied. Also, I really can't sleep on my back and I'm not sure if it's as effective with my face pressed against the pillow even if I wait a bit before going to bed after applying.
Girls Blog 2015
Submitted by Several_Newt_2049