Revised ITR-5 after original ITR was already processed

You Can not cancel the filed revised return.

you should go for further revision of return.

you can revise any number of times till time lasts. 

That's Okay Amlan

Okay.. Thank you for your valuable time & guidance!

We had incorporated our LLP on 5th November, 2019. We are preparing our Form-11 up to 31st March, 2021 for the 1st time. 

Which date should I put in "1.(b) - Start date of financial year for which annual return is being filed" in FORM-11?

05/11/2019 or 01/04/2019?

As per my understanding financial year could be less than a year or it could be more than a year.

here in your case it is less than a year and you can put 05.11.2019. because your financial year started from this date only.