1.Yes, this substance is called Aminorex, and is active, but the effects are mixed, some like it, most do not. Is is also very unhealthy, causing heart problems.
2.Unknown bioactivity as far as I know, but Lilienthal said long ago that he suspected it would be "interesting" as most methoxylated subtitutes on phenethylamines are.
3.Mexamine is an entirely different compound totally unrelated to these structures. I don't see how one could produce an oxazoline from a tryptamine.
https://www.thevespiary.org/rhodium/Rhodium/chemistry/mexamine.html
As for midodrine, yes, you could use it to produce the 4-desmethyl aminorex analog, and as far as I know, this compound is untested as well. It has never been reported HERE at least.
PrimoPyro
Will perform sexual favors for females in exchange for 1,2-dimethylaziridine. PM for details.