There appear to be 2 parts to your question.
In general, if you receive an incentive to sign up for an account, that is taxable income and could be reported on a 1099-MISC or 1099-INT, and you must report that as taxable income. For example, XYZ bank promises you $500 cash back if you get their credit card and use it for 3 months. That's taxable income.
As a practical matter, banks must issue a 1099-INT for interest income over $5 and any company must issue a 1099-MISC for miscellaneous income over $600, so a lot of credit card companies that offer cash incentives less than $600 don't issue the 1099-MISC. That means the IRS is not officially notified of the income, but it is still taxable to you and you are on the honor system to report it correctly.
"and was gifted a stock from robinhood"
So if Robinhood paid you an incentive for opening an account, the value of that incentive is taxable income.
Suppose the stock was worth $5/share and you got 1 share. You pay tax on the $5 of income. That makes your basis in the stock $5, so if you sell later for $6, you have $1 of taxable gain. If you don't pay income tax on the value of the gift, then your basis is zero, and if you later sell for $6, the entire $6 is taxable gain.
"I bought cryptocurrencies...and I don't sell them"
Buying and holding cryptocurrency is not reported to the IRS and is not taxable, you may owe income tax if you later sell or use the cryptocurrency for a gain.
