Support Group award and backpayments question

Hi, apologies if this has already been covered , I can't seem to find any info.

After almost 9 months since applying for ESA I have finally been awarded payment and I have been placed in the support group. I cannot express my thanks enough to the people running this site for the advice booklets and help.

My payments , however , are from July 16th until Dec 2nd 2021 and I assume I will be reassessed in December.

My question is , am I eligible for a backpayment , as my claim was sent in on Dec 11th 2020 and I recieved zero ESA payments until this week. ( Sept 2nd). So just to be clear : am I entitled to payments from the date of my original claim or do I just put up with having nothing for those 9 months?

I was able to claim UC ESA for 6 months ( April 2021 -Sept 2021) as I was previously working and had paid NI. This is just a one off NI related payment of £74 per week and expires after 6 months.

Once again, my heartfelt thanks to the dedicated folks who work on this site, without your help , I wouldn't have been able to do it. It has been hard , due to my health but I wouldn't have stood a chance without your help.