Question regarding PS4 service

[Tsubaki75]

You shouldn't need the disk at all. If you remove the disk and uninstall the game on the ps4 then go to your library you will be able to re-download it thru there without the disk in the drive and won't need to have it in to play at all.
As far as your friend goes yes you can use the same acct on ps4 and pc, he will have everything except for things that are stored on local memory aka hotbar setups, hud layouts, and macros ect