Hi, just got a theory. If i have a gpd for lets say gears of war 3, make a backup of it. So i have 2 of the same gpds. I mod one of them and use it on my profile offline to unlock an achievement. Then i take that gpd off and attach my unmodded and unchanged gpd and go online. Would i get banned for this? As there will be no changes to the gpd?
Nope. Though your theory is kind of confusing. Achievements that are unlocked are stored on the GPD. If you unlocked one on your modded one then switched that GPD to a normal one you would lose the unlock anyway.
As Yumiyashi said the chevo's are stored in your GPD if you don't connect to XBL on the modded GPD then yes you will loose that chevo when you load the UN-modded GPD. however if you connect to XBL with the modded GPD on your profile it will be there forever as once connected o XBL it will update your profile data along with the modded GPD. so if you connect to XBL with the modded GPD it wont matter whether you replace the original or not as it will just recover the data back from Microsoft anyway. as with any modding especially GPD modding there is always a risk of being banned but not likely if you are careful what you are modding. unlocking 1 or 2 chevos is not likely to get you banned just don't go overboard and unlock a full 1000G of chevos lol. Also make sure that the chevos you are unlocking are not online cevos as they can be easier tracked than offline chevos.
Thank you both so much for your responses. I understand gpds better now. I had no idea gpd sotred the achievments aswell. Though it was just save data. I just wanted to mod gears of war 3 gpd so i was 1 match away from seriously but it seems like too big a risk now. +repped you both for clearing things up.