If something is not working, or you have a question, write to comida.giampaolo@gmail.com. We answer in English and Italian.
No. The three games come back on their own after two hours, with no action needed. The video is only for people who do not want to wait. The daily challenge is always free and never uses up a game.
If you linked an email address to your profile, no: reinstall, sign in with email and password, and everything is there. Without an email the profile lives only on that phone. You can link an email at any time from Settings.
On the sign-in screen tap "Forgot password": a message is sent to your registered address. If you cannot find it, check your spam folder.
Only through the friend code, which you find on the Friends screen. There is no search by name on purpose: that way nobody can find you — or a child — by scrolling a list.
Settings → "Delete my data". It removes your name and results from the online leaderboards. Or write to the address above and we will do it.