You seem to be asking, how can you claim the AOTC a 5th time.
You can't.
For the 5th year, you can claim the Lifetime Learning Credit (LLC) instead. Alternatively there's the Tuition and Fees deduction (TFD). Most people come out better with the LLC.
As to your specific question: Can I apply his spring 2021 tuition to the 2020 tax year since it occurred in the first 3 months even if it isn’t reported on the 2020 1098T? Yes, but only if you actually paid it in 2020. It only takes $4000 of total expenses to get the maximum AOTC. Most people come out better saving some of those expenses for the LLC in 2021.
