trello
My Trello password is remembered by the browser, but I do not remember what email I have specified when I registered the account. So I can't login anywhere else, neither can I use forgotten password functionality.
EDIT:
A helpful commenter pointed out that the second question is discussed here
I think you probably don't need to.
I did the same thing, because I didn't notice the Google option at first. When I logged in with Google later, it showed me the same information as with my original account.
Just to make sure, I logged out, then logged in with my original account (Gmail address and Trello password), and it showed me the same information. Apparently if you use the same e-mail address, it automatically associates the two.
There's an option in your Account settings, just go to https://trello.com/username/account or go to your profile to set your account settings.
Best Answer
https://trello.com/my redirects to your account profile. You can see your email address there.
You can see other settings at https://trello.com/my/account.
Per the comments and your edit, the other question is discussed in another place.