Priority date clarification

[kml1278]

Hi,

I am in my 8th year of H1B , have I-140 approved with one of my previous employers and current employer just initiated GC.

If I change to a new job now  and if they delay starting GC , 

 

1) can my visa be  extended when it close to expiring with the I-140 that was approved  with one of my previous employers (assuming its not revoked/cancelled).

 

2) The priority date, can it be retained if job titles changes?  

previously it was software engineer and new job it will be applications architect.

 

 

regards,

aravias