Rather than tapping the “gears” icon from the Inbox, tap a conversation to go into Conversation View and THEN tap the “musical note” icon. You’ll be able to set a wallpaper for the individual contact instead of for all conversations.
You can’t. You need to verify with the email you signed up with. Otherwise we can’t know that you’re you!
If you know your password and want to CHANGE the email assigned to your account, and THEN verify it, just log in and then go to Options and click on your email address. Enter your new email in the space provided and click “resend”.