I bought this Xbox game for a friend - I redeemed by mistake (new to all this) How can I...

If you head to the game online and the you can buy as a gift on that.

Then enter the email yours or theirs. Also the code for a new one will be sent to you and just send them the code.

You would need a full paid subscription in order to download the 360 games with gold games. Trials do not actually change your account status to gold. One games require a subscription in order to keep the games for free so they work a little differently.
For a refund/exchange, you would need to contact support and speak to billing. http://support.xbox.com/contact-us

I bought an Xbox one yesterday it came with 3 games the code for the three games as invalid I bought an Xbox one yesterday it came with three games the code for 3 games is invalid how can I get a new code to redeem my games

You would want to check http://commerce.microsoft.com to see if it will let you start a refund there. If not, you'll need to contact support and speak to billing. 1-800-4my-xbox if you're in the US/Canada or http://support.xbox.com/contact-us

Hi, I hope you're doing great out there. I am an Independent advisor and I am here to help you in regard to your concern.

Make sure that the code is not yet redeemed and you can try to request a refund by signing in to https://account.microsoft.com/billing/orders and then copy the order number. Once you have it simply go to the refund webform link here: https://support.xbox.com/en-US/forms/request-a-...