Marketplace games on second HDD

The reason to make this topic is to ask whether having Unreal software installed on second HDD, connect it to some other computer with exceptionally fast internet speed, downloading a game, bringing back the HDD home and connecting it to my main machine work? I don’t want to be flagged by Unreal Store so I thought I should ask this question before doing that.
My cousin has really fast internet speed whereas I don’t have an internet connection at all. All my internet related activities are done through mobile data connection. It’s enough for small games. For like under 15GB. But GTA 5 is 65GB or more I think so I can’t afford to pay for that much data. Also, fiber would be much faster than wireless mobile data.