if i upload my game for people to purchase and i do update to it, will some who already bought it be able to get the new version or they are force to buy it again? i think they can without repurchase, i just want to make sure.
The buyer is given a download key for the whole project. That does not change, if the price of the project changes, or if files are changed. That means the buyer can download all regular files on that project.
The exception is individual priced files. Those are compared to the purchase amount to determine if they can be downloaded.