1 - Migration from RU6 MP2 - RU7 MP1 - Is it a one time upgradation or first to RU7 and then to RU7 MP1(twice)?
Two step upgrade, it should be upgraded to RU 7 then to RU 7 MP1. Why not upgrade to SEP 12.1 RU 1.
2 - Is RU7 MP1 a supported migration path for SEP 12.1 RU1?
YOu should not be upgrading SEP RU 7 MP1 t0 SEP 12 RU 1.
2nd Scenario
1 -Migration from SEP RU6 MP2 - SEP 12.1 RU1 - Is it a one time upgradation or first to SEP 12.1 and then to SEP 12.1 RU1(twice)?
It's one time, you can directly upgrade to SEP 12.1 RU1
2 - Is there any additional licence cost is required for upgradation to SEP 12.1?
if your company is having valid license, the upgrade is free.