I know this isnt the serpentine belt and that the 2012 ford escape has a timing chain; so, what belt is this? And how often should it be changed? Thanks in advance.

 

Thats the water pump belt.
Belts do not need to be changed on a particular schedule, they should be changed based on condition, that said if you want you could replace all drive belts every 100K miles and not have to worry about them.