Samsung galaxy light can I remove the sd card card while it is off. When I install the sd card would I have to remount the sd card when I turn the phone back on
Welcome to Android Central! If it's completely powered off, you can remove the card without any problems, because there's no way any kind of read/write process could occur while taking it out. I don't think you'd have to remount it if you reinsert the card, then power back on, but I've never tried it before.
Welcome to Android Central! If you're prone to forgetting important things like the password to the phone you use every day, then I suggest in the future you write the password down and keep it somewhere safe and secure at home.