You can! With a few caveats.
[asklemmy](/c/[email protected]) becomes asklemmy
However it won’t work if your instance doesn’t know the community exists. In those cases it needs to be searched for in the usual cumbersome way, but after that the relative links should work.
I think creating too many accounts as you try to find a home and figure out what instances are is a normal thing. I certainly did it as well 😂
You can think of each instance as a separate reddit website. The magic of the fediverse is all these separate full on websites are still the same thing and can interact with each other!