Hey guys. I was wondering what it would need to create redeem/ bonus codes system. I mean like generating random code and storing its information somewhere. And then people can insert that code for unlocks ect. Thanks 
If you know the codes before you ship your game then you can just have them in your code or saved in a file in the game and read later to check for validity. Then you can manually distribute them when you want or have the game give them automatically at certain times.
This obviously gives the possibility of someone finding the codes in the game. You could go into encryption to secure it too or you could do it over the net.
Have a service running that validates entered game codes. Using this means you control all redeemable codes. You can add or remove or flag certain ones. This does have the downside of requiring a connection.