Extension Tier 2 in the period of overstay

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Hi all,

Due to a long time waiting for the interview, I am now in an embarrassed situation that my visa will be expired on 14th Jan. I have got an offer and submitted my ATAS application on 17th Dec 2021. It seems very difficult for me to have the certificate and submit my visa extension on time. Here I have serval inquiries that:

Is it valid to submit my visa application during the 14 days grace period without applying the "exceptional assurance"?

If my plan is to stay in UK legally, is it OK I apply the exceptional assurance within 14 days and apply a new visa in this period?

If finally I have submitted my new visa application during the 14-day overstay or exceptional assurance, does this mean that I broke the 5-year ILR routine law and need to recount the time starting from the new issued visa?

I appreciate your advice and help!

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Anyone can help me? thanks