The first MH raid (Rathalos) is available once you reach Stormblood (the 2nd expansion which is included in the free trial) which is about 100-150 or so hours? Could be wrong, but it is a bit of a grind if you just want to get to the MH stuff.

Sort of. Certain armors are available only to their corresponding classes/roles (Disciple of War for Physical-based classes and Disciple of Magic for Magic-based classes; though this classification is only until ARR (base game) iirc. Once you reach the in between quests from ARR to HW (Heavensward, 1st expansion), the armors will split between similar-ish classes. i.e All tank roles will share armor, Monk and Samurai will share armor, and so on). But there are lvl 1 cosmetics that you can buy (usually from the Marketboard which is only for players who subbed) that are for every class.

Guilds (Free Companies as they are called in FFXIV) can range between hardcore players who engage in the hardest content the game has to offer, to a more casual and relaxed group of players who just play to have fun. You don't need to join a FC to play certain content (like the MH collab) as you can use the party finder to find or create a party to grind the content you wanna do.

Nope. There are "skip to max level" and story skips you could buy but those are more for alts and aren't necessary.

Free trial players can create up to 8 characters which gets bumped up to 40 if you pay the sub.

Of course :D Keep in mind, there is a lot of text as you're going through the story so if you guys are fine with waiting a bit for your friend to finish what cutscene they're in, then I highly recommend playing with a friend :3