Is it possible to change from free version to $30 after submitting taxes

No, you can not change from free version to $30 after submitting your tax return.  If you need to change to the $30 version to add tax information that is not supported in the free version you may have to file an amended tax return.

If you have filed your tax return and then discover that you have information to add you will have to wait until the IRS either accepts or rejects your tax return.     

If the return is rejected you will correct the error that caused the rejection, add thr information and refile your return.     

If the return was accepted by the IRS then you will have to file an amended tax return using Form 1040X to add the information to your tax return.   

This link to the TurboTax Help page  How to amend (change or correct) a return you already filed provides information on how to amend your tax return.