Can I access my original tax return before I amended it on TurboTax

maybe. it depends on what you are looking for. column A of 1040X shows the original return amounts. column B shows the changes. it may be unwise to change the amended return because when you do the 2021 return certain items will be pulled from the amended return.

Always print a copy of your completed tax return for your records, and review it carefully before e-Filing.
You will need it if you are audited by the IRS, or to amend if a TurboTax update changes your return or for any other reason,

AND, to find your AGI next year.