Yes - you can downgrade versions In TurboTax Online, as long as you haven't paid yet (or registered in a free version) - but please bear in mind that you will need to clear any data which you have entered, and start over in the other TurboTax version.

Please see the following TurboTax FAQ, "Can I switch to a lower-priced version of TurboTax Online?":

https://ttlc.intuit.com/replies/4248526