If you never filed, you don’t file an amended return, you file an original return. There is no deadline, but any refund that might be due won’t be paid if the return is filed more than 3 years after the due date.
Amended returns to correct a previous return can be filed any time, but any refund that might be due won’t be paid if the amended return is filed more than 3 years after the due date, or more than 2 years after the original return was filed if it was filed late.
I would recommend filing a correct return so that all the correct information is on file, even if a refund can’t be paid because of the time limit.
I can’t address the body of your question because it is too confused and non-specific. Whether or not you can deduct crypto losses depends on how you use the crypto (to invest and hold, or use for purchases). If you have crypto investments, self employment, and wages, that should all be reported on one single tax return that combines all your income, deductions, credits and dependents.
