Welcome back!
With the $79 subscription the software works for one year. Then you would need to renew for another year.
Yes it does have STL export. The choices for subdivision are 1, 4, 16, 64, 256, 1024, 4096 and "variable" OBJ has those also and some people find OBJs work better with their 3D printer software.
You can run any previous subscription version with a current license so you could keep using v18 even after v19 has been released.