Join new employer with old emp I140

[whoami191]

Hi,

I completed my 6 years on H1, I joined my current employer (empB) 18 months back with I140 from previous employer (empA) so I got extension till 2014 Dec when I joined them in 2011 Dec. I dont have I140 from EmpB yet, they have just started the perm.
1. If I want to switch to EmpC then will I be able to use EmpA's approved I140 to get extension of 3 years on a new assignment? Or do I need to get I140 approved from EmpB to be able to join EmpC.
2. Say if I go out of project and unable to find one soon, instead of going back to India can I convert to Student visa?
    a. For this do I need to join a university or any institute? Can I convert to student visa from H1 at any point of time of year?
    b. I read somewhere that if GC processing is going on then converting to Student visa is not easy? Is this true?
    c. Is it easy to convert back to H1 from Student Visa after finding a job? In this case do I need to file new H1 or would be able to use existing petition?
    
Please advise.

[omshiv]

You can get extension from Employer C based on the approved I-140 of Employer A. If you are out of project, your employer needs to pay you while you are on bench. If they dont then complain to DOL and fix them up. Its not advisable to join some Univ as student on the bench period. Rather I would advice you to do COS on either B1/B2 or if you are married to H4.