Article for those who dont want a video: https://www.gamesradar.com/games/final-fantasy/after-13-years-a-new-version-of-final-fantasy-7-is-replacing-the-current-version-on-steam-and-square-enix-hasnt-explained-whats-different/
Steam: https://steamcommunity.com/games/39140/announcements/detail/514107648813039663
Square Enix has announced a brand-new version of Final Fantasy VII for Steam. This is not a patch. It’s a replacement.
The existing release will be renamed FINAL FANTASY VII 2013 Edition, while a new version becomes the default Steam listing. Existing owners get both versions for free but save files will NOT be compatible between them.
Well, you have to do it only once. You don’t need constant internet connection. I mean you need internet to download the game, so just run it once and then you can play it offline without internet or wifi.