1).Is there principle differences between these two systems and their operations?
2).According to my knowledge it is used to exchange info between aircraft and ground( may be satellites will get involved). Is there any other uses from it?
3) I have heard that in MH370 B777 aircraft pilot had turned off it and even if it is turned off ACARS maintains a link between the aircraft and ground and Inmarsat uses that link to locate the aircraft by using BFO (burst frequency offset) and BTO (burst time offset). How to turn off the ACARS as that pilot did? Is there a way to turn it off permanently?
I know it is a bunch of problems and please help me to solve my unexplained problems...

Thanks a lot.
Regards.
Skywalker92.