2. We've talked about that before and I can't think of anything else except do consider subscribing to PS Plus if you go for PS4, it is required if you want the multiplayer experience for PS4.
3. I think Daniel answered that.
4. I think Daniel answered that as well, but since I'm not sure: Your saved files are tied to your account. If you switch account, you have to play it like new.
5. If the game is cross-buy (meaning you buy for PS4 game and you get the PS3, PSvita version as well, etc) then you can probably download it to another unit. For saved files, it depends if the game has a cross save functionality like for example; Borderlands 2 and Counterspy. You have to check the game's details before you buy, there's a "Playable on.." at the right of the game page if you're checking the PS store on your browser.
6. I checked. Thought you can't treat my words as gospel, I think Samurai Warriors 4 - II is some sort of special edition. The game with added content.
What's with the fascination with Samurai Warriors?
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)