Hope this visual helps
"PS5 only version - CAN or CAN'T play with PS4 version players ?"
No, you can't. You can only play with people playing the PS5 version of the game.
"PS5 X-factor version - PS5 console players CAN or CAN'T play with players on PS4 consoles"
The X-Factor version gives you both the PS4 and PS5 versions of the game to download. They are separate games. You CAN play with PS4 players if you download and play the PS4 version of the game that you get with X-Factor edition.
"You would need BOTH consoles (PS4 and PS5) for the Dual Entitlement to work. YES or NO ?"
Both PS4 and PS5 users can buy the X-Factor edition, but ONLY PS5 consoles can download and play both versions (PS4+PS5). You can buy it on PS4, but you'll only be able to play the PS4 version. If you later get a PS5 you'll still have access to the PS5 version to download (as well as the PS4 version).
