1. Startup costs must be claimed in the year you started the business. You can amend your 2020 return and put the business and startup cost on that return.
https://www.irs.gov/pub/irs-pdf/p583.pdf
2. Yes, I think since 2020 and 2021(?) have been filed, I would consult a professional to determine what costs are capitalized and what can be elected to be claimed immediately. Also, they could prepare and amend 2020 for you and if necessary 2021.
**Disclaimer: Effort has been made to offer correct information; but due to the discussion forum limitations, the poster disclaims any legal responsibility for the accuracy of the poster's response**
