h1b transfer before Oct 1st

My H1B application was luckily chosen this year, and I’m still waiting for the approval. Now I got an another job offer, similar company similar position but much higher salary. So I was wondering if I can do H1B transfer after the approval but before Oct 1st?

I am in US.

I haven’t started to work yet and am graduating in May. My OPT is on the way and I expect to get it in June.

I saw some discussions here and there. Some says you need 2 month paystub from old company. Some says you don’t.

To summarize, my questions are:

  1. Can I do the transfer?

  2. If in case the transfer was denied, but I make sure that my old company doesn’t know all this, would there by other consequences? For example, would it still be ok to go to work in the old company?

  3. If the transfer is successful, can I use my OPT for the new company (from June to October), or do I have to wait until Oct 1st?