H1-B extension solely for recapturing vacation time

My H1-B visa, I-797 and I-94 ends on Aug 23, 2018. I recently went on a vacation for 5 weeks and hence my 6 year maxout is on Sep 28, 2018. I don’t have any plans to stay even a day longer. Can I apply for extension (normal processing) and stay here for those 5 weeks?

If USCIS takes my extension (normal processing) a little later, say by Oct 2018, will they reject the extension because maxout is over? In that case, will they consider my stay from Aug 23 - Sep 28 as illegal? Or will they just abandon my extension processing request?

If my extension is put in RFE between 8/23 and 9/28, I will not have sufficient time for re-submission. In this scenario, what will I have to do? Will they consider my stay from Aug 23 - Sep 28 as illegal?

If my extension is put in RFE after my maxout and departure on 9/28, what should I do? What are the consequences? Will my stay be considered as illegal?