Status of Tier4 after getting Tier2 and SOC Code

Hi,
My employer is going to apply for Tier2 for me and my Tier4 is also valid. I'm getting a SOC Code which I plan to change in the future. I want to ask the following:

• 1)Will my Tier4 expire right after getting Tier2 or will it stay valid until it's original expiration time?
  2)Can I apply for jobs while I'm working for this employer on Tier2 and still holding a valid Tier4?
  3)The job I wanted has a different SOC Code. Will I be able to apply for it without RLMT in this situation?

thanks.

The T2G leave, when you get it, will replace the T4 leave