If you came in the US in 2016 on a F-visa, you are considered as exempt ( not counting days) hence a nonresident for tax purposes for five years ( 2016-2020). You would be filing a Form 1040 NR for your 2020 tax return. Starting from year of 2021, you would start counting days being present in the US. If you stay for at least 183 days or meet the Substantial Presence Test , you would be a resident and file a Form 1040.
You cannot use TurboTax to file your 2020 tax return and will be suggested to use Sprintax.
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