This question has been answered by multiple community members. See the first response.

Backend and frontend users are the same, just with different access permissionsThe only password reset feature I know is the one at the manager login screen. What other reset method are you referring to? If you mean the database method, I'm hoping for a fix to the frontend reset.
create another install of MODX (or use one you have already) where you know the username and passwordBob, how can another modx install help me with this install?
login into different browser, because u are probably logged in with adminTried with different browser. Same problem. How could I be logged in as admin, if i cannot login?
create another install of MODX (or use one you have already) where you know the username and passwordBob, how can another modx install help me with this install?
As a last resort, you can always create another install of MODX (or use one you have already) where you know the username and password, then go into PhpMyAdmin for both sites and cut and paste the working username and password, hash, method, and salt into the appropriate line of the modx_users table at the problem site.