refactoring in GIT

Hi,
 I'm new to GIT and have two questions about code refactoring. 

#1. I want to refactor class A into few classes B,C,D. How should I check them 
in and mark class A inactive so that development on A stops? Note, I do need A 
stay in repository for backward compt. with prior code releases.

#2. [related question] What if another developer already had A in his local 
repository, made changes and wants to commit after me. I just made A obsolete. 
Does he have drop his changes and take B,C,D from me and/or merge?

Sorry if this question was already answered, pls point me.

Thanks,
Eugene