Does this come with the mirror bracket or backing plate?

Glass lens only. You'll reuse your existing mirror assembly frame and backing—this is a direct glass replacement.

Will this fit if my mirror housing is cracked?

This replaces the glass lens. If your mirror housing or backing plate is damaged, you'll need to address that separately or source a complete mirror assembly.

Do I need adhesive or fasteners to install this?

Installation method depends on your existing mirror frame design—some use adhesive, some use mechanical clips. Test-fit before committing to your chosen mounting method.