How long would it take for an 87 year old man to wake up after 2 hours of sedation?

No real answer . There are many variables including what drug(s) were used and the patients kidney and liver function. I would think 2-6 hours is a fair range.
Depends. Depends on a multiplicity of factors. Pre sedation condition. Type of sedation used. Other meds given. Ability of liver and kidney to clear medication. Tolerance to meds, etc. The person administering sedation should have a real good idea of the factors involved.