In order to determine the right processor that you have on your system, I would suggest running the Intel® Processor Identification Utility.
You can download the Intel® Processor Identification Utility at:
This tool will properly recognize the processor that you have on your laptop.
Regarding the 2nd question, first of all, you need to make sure that the laptop supports the processor that you want to install, this is if the processor is not soldered to the system.
Only the laptop manufacturer can tell you if the processor is compatible or not with a particular laptop system.
To check the differences between those 3 processors please check this link:
It seems that there is not much of a difference.