H1B Transfer approved but sticking with same employer things to do

[atryun]

Hello All, i believe a lot of times this same questions has been asked, but i get different response from my companies immigration attorney.

Working for employer "A" my current H1 is valid till Sept 2016. I got an offer from employer "B" and they processed my H1 and also got it approved from USICIS. I am now thinking of staying with Employer "A" for various reasons.
My questions:
1. Does employer "A" have to reapply for my H1 Visa and get it approved ?
2. Does employer "B" have to do anything (cancel the H1 they got approval for) ?
3. In this case I have not told my Employer "A" about the new company. So do i need to inform about a new H1 filed on my behalf by another employer ? If i dont say anything will it bring in any complications later on when they try to extend my H1 ?

Appreciate any useful response.

thanks,
Arun