Age problem

If changing your birthday ("Edit your personal info") isn't working, you can try contacting Xbox Support (phone/chat), they
might be able to help you. You may have to provide some proof of your age for verification purposes, but just see what they have to say.

Post back with updates!

Phone (US/CAN): 1-800-4MY-XBOX

Chat: https://support.xbox.com/contact-us

ya hate to break it to you Internet expert but that doesn't work for Xbox accounts (confirmed by forums support agents)

Unfortunately once set op your age of ykur account cannot be changed

If changing your birthday ("Edit your personal info") isn't working, you can try contacting Xbox Support (phone/chat), they
might be able to help you. You may have to provide some proof of your age for verification purposes, but just see what they have to say.

Post back with updates!

Phone (US/CAN): 1-800-4MY-XBOX

Chat: https://support.xbox.com/contact-us

The demo is restricting you to legal limitations. US law prevents minors from being show mature advertisements, which includes demos. However, you can still play the demos. You could always download it using the parent account over your account, in a way
giving authorization (though you could donwload it on any account and still play).

It depends, is it a Xbox message that is restricting you, or one from inside the game? EA games may require the user to be older then 13, while if it is an Xbox error, it may be related to unrated content settings on the console. You can check that by going
to Settings>Family>Ratings & Content>Unrated. (If Content controls are on, you will need the 4 button passcode in order to change the settings.)

Age cannot be changed on Xbox Live. When you become legal adult in your country the option to promote your account to adult will become available. If you start over nothing can be moved including content (season pass items are on that gamertag). You can
change your privacy & online settings to adult and to enable purchasing. This has to be signed off by the parental password that set up the account though.

Thanks to google translate:

Wiek nie może być zmieniony na Xbox Live. Kiedy się prawnym dorosłych w kraju rozwiązaniem, aby promować swoje konto, aby dorosła będzie dostępny. Jeśli zacznie się nic nie może być przeniesiony w tym treści (pozycje Season Pass są na tym tagu gracza). Możesz
zmienić swoje ustawienia prywatności online i do dorosłych oraz umożliwienie zakupu. To musi być podpisane przez rodziców hasło, skonfigurować konto chociaż.