To access your current or prior year online tax returns sign onto the TurboTax website with the User ID you used to create the account - https://myturbotax.intuit.com/

When you sign onto your online account and land on the Tax Home web page, scroll down and click on Add a state. 

This will take you back to the 2020 online tax return.

Click on Cancel Amend on the left side of the online program screen.

"Cancel Amend" will remove the Form 1040-X, but it will not undo the changes that you made for the amended return. You have to go back to any entries that you changed and manually change them back to the way they were before you amended. See the following FAQ.

How do I cancel or undo an amended return in TurboTax Online?