Unfortunately, Tetris turned into some weird kind of adware, a few years ago, with no option to just pay a bunch of money, and not be bugged (I would have been happy to do that).
The Tetris Company is very stingy about how many licenses they hand out, and mobile games they do license are always terrible. Your best bet is probably to take advantage of the Delta emulator that's now available on the App Store, and use it to play a high quality Tetris like Apotris: https://akouzoukos.com/apotris
I would also recommend try making a Tetris clone yourself. Tetris is a sufficiently simple game at its core, and with the tools available today it's a rewarding and painless experience.
I assume you won't get in trouble unless you try to distribute it widely.
Unfortunately, Tetris turned into some weird kind of adware, a few years ago, with no option to just pay a bunch of money, and not be bugged (I would have been happy to do that).
I haven't played in years. :'(