H1-b renewal question, thank you for help

I'd like to renew H1-b soon for the next 4th-6th year. I will stay with the same employer. I have two questions about it:

If I don't recieve the approve notice in time, can I continue to work (since I the case and it is pending) or I must wait until it is approved?

When should I start the H-1B extensions? (How many months prior to the expiration?)

Thank you for your kind help