working on H1b extension receipt

[blue10]

I have a very basic question, but want to make sure my understanding is correct. My current H1B visa for the first 3yrs will expire on Sept 6th, my employer has applied for extension and got the receipt notice. It's been 3 months but I haven't received I797 yet. I'm guessing i can continue working in H1B using the receipt notice for atleast 6 more months even though I don't have the I797. My other question is, if by any chance my application gets issued a RFE, would i still be able to continue working using the receipt notice or it would forfeit my work eligibility.