TurboTaxAshleyRose provides an excellent explanation below:
Ok, You can now downgrade with the Clear and Start over feature here, https://ttlc.intuit.com/questions/2586254-how-do-i-clear-and-start-over-in-turbotax-online,How do I clear and start over in TurboTax Online? but, please keep in mind, that different TurboTax handles different tax situations and their associated forms.
Here's how you can start over in either the same or a new Online product you choose, as long as you haven't paid for TurboTax Online.
NOTE: Starting over clears all of your current entries. All entered information will have to be re-entered in the new Online product you start over in.
Once your new TurboTax Online product is selected, you can return to your taxes.