I-94 expires 08/22. L1B extension paperwork sent. No receipt yet. Will working post 08/23 pose risks to H1B stamping in Sep end?

Deatils: The plan is to work from 08/23 - 09/23 in USA. Then travel to India, get H1B stamping and travel back on 10/05 on H1B. However, since L1B Extension paperwork was sent to USCIS on 08/14 and Receit number is not available yet, so wondering: 1) After 8/23, Will I be out of status till receipt number does not come in? 2) What risks this carries for H1B stamping in India during September end?

You should have the receipt for the extension by then, that would allow you the automatic work authorization for timely filed extensions.

If not, see if you have evidence that the case was delivered (USPS certified mail, FedEx). If you don't have that, you should not work beyond the I-94 expiration date.

Consult with the company immigration attorney to confirm. Good luck.