Bought Horizon 4 digital, play offline?

Hi, yes you can play it totally offline if you have set your xbox as 'home console' (this is beacause they need to verify in some way that the purchase is related to your account and console). More info here: https://beta.support.xbox.com/help/Hardware-Network/connect-network/using-xbox-one-offline

Keep in mind that FH4 has a strong online component and you cannot enjoy it 100% playing offline

Do you have Forza Horizon on a physical disc, or as a digital download?

Only digital downloads provide ownership for both systems.

Also as Ackis already mentioned, make sure you bought Forza Horizon 4 on the same account that you use on Xbox One and PC.

If you bought it on a different account that has your console set as "Home Console", all accounts on the Xbox One can play the game on that console, but not on the PC.

Only the account that actually purchased the game digitally can download it on Xbox AND the PC.

Forza Horizon 4 can be bought and played without gamepass, yes.

Yes. Horizon 4 is a Play Anywhere title so if you purchase it digitally on the One or PC you can play it on both.

I have "Xbox One S All-Digital Edition" console. I want to play GTA V completely offline once I download the full game from Xbox store. While looking for this, I found some unclear answers stating, I can play offline but I need to be connected to
the internet EVERY time I start the game(Perhaps while logging-in to the console). Is it true?

I have downloaded gears of war 4, Halo 5 and Forza Horizon 4 which I can play
completely offline. These games don't require the internet even while logging in to the console. Is this the same for GTA V too?

P.S: Link to the game on Xbox store would be really helpful.

Yes, I can play GTA V completely offline.