No, you will not be able to return to the free product after the upgrade.
Your teacher expenses are deductible even if you take the standard deduction. You do not need to itemize to take the educator expense adjustment.
The TurboTax Free Edition does not include Schedule 1, which is required to list those expenses.
How do I list the teacher expenses without itemizing?
When I answer "Yes" to "Did you spend your own money as a teacher in 2019?," I can't enter the information without upgrading to Live Deluxe.
Is there another place to enter these expenses?
No, there is not another place to enter them. You are not required to upgrade to Deluxe because the expense is being itemized, but because it is on a form (Schedule 1) that is not in the Free Edition.
You will still take the standard deduction and you will get the adjustment for your classroom expenses. But to do this, you must use the Deluxe or higher edition.