The IRS doesn't take your legal status into account (and if you work, they don't inform on you, as far as I'm aware. They just want their tax money.)
As a US citizen or resident (passing the substantial presence test) you must report and pay US income tax on all your world-wide income, even if you have income that is also taxed in your country of origin (such as investments). If you are taxed in another country, the US will give you a credit or deduction to reduce the double-taxation.
Here is the substantial presence test.
https://www.irs.gov/individuals/international-taxpayers/substantial-presence-test
For 2021, you are probably a non-resident alien. You only owe income tax on income that was paid to you while living in the US. You can use your SSN even though it was issued in 2023. However, Turbotax does not prepare non-resident tax returns, you will need to use different software or see a tax professional.
https://www.irs.gov/individuals/individual-taxpayer-identification-number
For 2022, you are probably a dual-status alien. As @pk explained, you file as a non-resident for the period of time when you were a non-resident and only pay tax on US-source income, then you file as a resident for the period of time you are considered a resident, and pay income tax on all your world-wide income. You can use your SSN. Turbotax does not support dual-status taxpayers.
For 2023, you are a resident of the US and you will file as a resident, to report and pay income tax on all your world-wide income. You can use Turbotax for your 2023 tax return.
Your filing requirements as a freelancer are the same whether or not you were an "official" business. Whether you are a sole proprietor or a single member LLC, you file a tax return that includes a schedule C that reports your gross business income, deducts ordinary and necessary expenses, and pays income tax and self-employment tax on the net profit. (If you formed a partnership, an LLC with more than one member, or an S-corporation, the rules are different.). You are required to report your income and expenses from your own accurate records even if you were paid in cash and made payments to others in cash. There are some good books on how to report and pay business taxes, or you may want to pay a professional to advise you for the first couple of years.
Don't forget that you also owe state income tax for 2021, 2022 and 2023, if you live in a state with an income tax.
