The most important thing is to get your 2020 and 2019 tax returns corrected with amendments. This is a common mistake for former dependents to make: assuming they're still dependents when they're not. TurboTax will take care of the first two stimulus payments as you do this on the 2020 return. Your stimulus payments will be added to your 2020 refund.
My understanding is that the first 2 stimulus payments were based on your 2019 tax return. So, make sure of your correct status for 2019, first. You may need to file an amendment for 2019 is that year is incorrect and then, file an amendment for 2020. You may get an unexpected 2019 surprise additional refund with any changes for 2019, which I would assume could affect your stimulus payments.
The 3rd stimulus would be based on you 2020 return after its filed, as corrected.
