19 attempts to land it from orbit, with many of those being onto boats. They had lots of "easy" success with low altitude test flights, and a booster isn't ever going to have people on it. this will.

going to be tough, hope it works!

The first stage of the Falcon 9 does not go to Orbit.

These test flights might be low altitude but the flip and landing is realistic.

I don't understand how the belly flop is even possible.

I'm far from a rocket scientist, but I thought that rockets were kind of like soda cans - very strong on the long axis, but not at all perpendicular to that.

If you make them strong in both directions, I wonder how that doesn't make them prohibitively heavy.

Well, sure that is generally what is the case. But of course the designer can design it as he likes depending on the situation.

Generally, of course this is more true when the stages are empty. If the tanks are pressurized, as they are during the whole flight, they actually become very stable in both directions.

Starship is specifically designed to survive a reentry (heating) into the atmosphere at an angle, just like the Spaceshuttle.