are you just trying to get an idea of the game and if you want to jump in or not? if so, give the free trail a try. it'll allow you to play up until the end of Stormblood expansion, up to level 70 for free.
regarding the 1.0/ARR stuff, it's been well documented already but if you don't want to watch any of the videos on it, here's a slightly shorter summary.
back in 2010, the original XIV was released. but due to a lot of issues, it ended up being super terrible. SquareEnix actually suspended charging the monthly fee for everyone while trying to fix the game. but even after they changed out the leader and placing Naoki "Yoshi-P" Yoshida (the current producer and leader of the game), the game was still consider unsalvageable. however, since this is a mainline FF title, SE just can't let it go down as one of the worst title of the company, so they accepted Yoshi-P's suggestion, and decided to "reboot" the game. they still worked on improving the original 1.0 version while also working on a rebooted 2.0 version. they were able to succefully merge the ending story of the 1.0 game into a new start for the game. the end result was "A Realm Reborn" (ARR). so when people talking about 1.0, they're talking about the version of the game that no longer exist. ARR is the base current game. I think XIV and No Man's Sky are the only 2 games ever that had came back from such a disastrous launch.
when talking about MSQ, that means Main Scenario Quest. that's basically the main story of the whole game. it's always the core of the game and you will have to play through it from start to the latest expansion in order to make progress for a lot of other stuff. and unlike some other MMOs, you don't really skip the base story (well, you could if you want to pay for story skip and stuff, but those are STRONGLY advise against) and go into the next expansion's story. you WILL have to start from the ARR story and progress it even if you got the latest expansion.
edit: as far as story goes, I think the main story of XIV is by far the best out of all the number FFs, with maybe XI giving it a run for it's money. that's mainly due to the fact that you can do a lot with it in a MMO format. while the ARR base story is nothing we had not seen before, the end of ARR really dial things up a lot and making you really hype going into Heavnsward. each of the expansions that followed had only bring the story to a higher high, with Endwalker being sorta like the "Avengers: Eng Game" of the MCU, concluding that line of the story and giving the game a fresh start into the next one.