Do I need game pass ultimate to play with friends on PC?

If the game is cross-play, then if you own the game, then you will need Gold or Game Pass Ultimate to play with your Friend on PC. Since the game is available on Game Pass, then you will need Xbox Game Pass to play the game if you do not own it.

Game Pass Ultimate is just a bundled subscription of Gold, Game Pass, and Game Pass for PC. So games downloaded from Game Pass will work the same as they do with standard Game Pass versus Ultimate.

Since Forza is a Play Anywhere title, you an download it on both the PC and console without needing Game Pass for PC or Game Pass Ultimate.

In short, no you don't need Game Pass to play it on PC if you have bought the game.

Game Pass (not the Ultimate version) has nothing to do with Multiplayer anyway as it just allows you to download free games etc. The Ultimate Game Pass includes Xbox Live Gold within it...however, PC players do not need Gold to play online. That is the biggest benefit of playing on PC, namely not needing Gold so saving money.

No, you do not need to upgrade to Ultimate. You only need that if you want Game Pass for console, pc, Xbox Gold, Cloud Gaming & EA Play in one package. If you just have Minecraft and want to play online with friends, then you only need a gold subscription. If you do not own Minecraft, then you can purchase it, or get Game Pass for console, and play the game using Game Pass instead.

Yes you can if the game is crossplay.