Does Microsoft file H1B transfer and H4EAD when we join them or they do only H1B transfer
H1b transfer will be done. H4 EAD doesn't need a transfer since the EAD is employer independent.
It is good idea to get h4 EAD extended along with h1 transfer. There have been many cases recently where people managed to get the h4 EAD renewed even though it was not due for renewal. You may ask about paying from your pocket for doing h4 ead along with h1 extension
Wasn't there a time limit eg 6 months before expiry for it to be renewed?
That depends. Are you from Bangalore?
No..