Need help plzzzz

ok so i want to change my password cos i think its too easy to guess but i forgot what my registered email is cos i made this account like 2 years ago or something... I have tried all my emails that i remember but they all say incorrect registered email.

secondly can u change ur nickname without resetting ur kdr?

and lastly plz tell me if to join rival factions thing do u have to leave ur clan?

thanks ppl =]