Stay with old employer after a visa switch

[Flid]

Hello.

I'm in a bit weird situation. Was on Tier2 visa for a year with one employer, decided to go to another job, applied to a new visa, my documents are in Home Office. Then I have a nice offer from the old employer to stay with them.
Let's imagine I accept it. What does it mean for my visa situation? I'm still working on the old job, even though I gave a notice, still have 1.5 more months till the resign date. Is there a way to return my old visa back? Or should we apply for it again from the beginning? If so, can I keep working with the old employer while the visa is getting ready?

Thank you!

[CR001]

If your new visa has been issued already, your old visa is cancelled and you would have to apply again for a visa to remain with your current old sponsor.

[Flid]

And if it hasn't been issued yet? Though the documents are at Home Office. Is there any way to interrupt the process, just force them to return all my documents back?

[CR001]

Withdraw and hope for the best that it is in time before a decision is made.

[Flid]

Thank you very much!

And if I need to apply for a new visa (which is a lengthy process) - I can't work with the old employer anymore?

My resign date at the current place - and of Oct. My start date on the new place - end of Sep (yes, I have up to 28 days to start, so it's all fine). How long can I actually work on the old place, if we cancel the notice?