Question: Buying the game...

[Naria]

Yes, each version and expansion of the game is a new purchase. FFXIV's next expansion, Heavensward comes out next month (also called to as 3.0). In order to access any of the Heavensward content and updates, you have to purchase the Heavensward software. The purchase of Heavensward will also give you access to all of the 3.0+ series updates over the next year or so. Of course also have to continue to pay a sub to access the servers. There is a combo pack available for both ARR and Heavensward you can purchase that will give you access to everything through 3.0.

If in the future you wish to change platforms to PC, PS4 or MAC you will have to repurchase the base game and expansions for that platform. You don't have to restart your character, however, as that is tied to your overall service account.

Out of curiosity is your sister's laptop an identical spec? If so, it should probably be able to run on your laptop. What happened when you tried?