MBA implications of pre-MBA role

Hi all,

Second year MBB going through MM PE recruiting. I've had conflicting reads on these questions so hoping you guys can shed some light. In a nutshell, I want to join a firm with the intention of staying beyond the associate role (I intend to go to b school). Would love some help with these questions:

1. What % of MM firms sponsor MBA?

2. What does a returning associate make after MBA vs a greenfield hire?

3. To those who are able to return as a VP post MBA, are majority of these people returning to the same firm they were at pre-MBA? Under what circumstances do you return as a VP?

4. If a firm has offices in both NYC and SF, how hard is it to change offices after returning from b school?

Thanks in advance guys