The enzyme products are generally meant to be a maintenance thing, i.e. if you use them regularly they remove light buildups of crud stuck to the inner walls of your pipes before they build up into being thicker layers of crud, which become blockages (or just reduce the effective inner diameter of your pipes).
This stuff might theoretically clear the right kind of total clog, but it’s likely to take a long time.
My advice is to get yourself a drain snake. Chemical clog clearing products “may” work, with various pros and cons depending on the type of clog. But physical removal of the clog with a snake always works, you will never run out of your bottle of snake, and provided you manage not to fuck it up so badly that you break it the snake is also infinitely reusable.
Just get one of those 50’ long jobbies you can put on the end of a drill. That’s just fine for most residential work and should only run you $20 or $30 at the hardware store.
Legal everywhere, no. Available everywhere, yes.