Do we have to watch the previous seasons to start this one
No but there are things you'll need to know from the first season to get the second. Most of the characters were introduced in the first. And there are major spoilers that will be important to understand why this or that.
I'm on episode 9, I really like the story, but ...damn I'm lost! It's like I'm watching Inception! Who's who?…
There's different timelines. There's also two parallels intertwining in one; wherever Jun Hee is. Yeon Jun is alive, only in body. Not in soul, not even in memory. Si Heon is alive but as two persons; in his own body, he's handicapped & in Yeon Jun's body, that lived just to complete this fate thingy. But actual Yeon Jun wasn't & can't be in love with Jun Hee because he's gay. And most likely dead in the car accident.
So I was right; Actual Yeon Jun dies once and for all, in that car accident. But Si Heon took over his body. when they let us know he's actually gay, and that piss me off because what's the point of adding that little fact to JUST KILL THEM THE NEXT MOMENT?!?!? I am sick, to the core, of having to have, even for a little bit, one or two gay/characters with tragic or sad endings. Sick and tired. It ruined the whole drama for me. Okay, it was wrong that Tae Ha didn't focus on the road, but Si Heon as Yeon Jun not even REMEMBERING TAE HA?! THAT HE LOVED HIM?? FXCK YOU.
If Si Heon is supposedly in Yeon Jun's body in episode 8, 1. why does he not have Yeon Jun's memories like Jun Hee had for Min ju??
2. How can there be two of Si Heon exactly? I'd understand if the Siheon who was accidented in 2002 in a bus accident and now handicapped was actually in a coma up until the point Koo Yeon Jun dies in a plane crash in 2022 but that's not actually the case and Yeon Jun right now believes he is Si Heon and has only Si Heon's memories. He doesn't even remember loving Tae Ha until he got into an accident. (this part is pissing me off tbh. Why do we have to always erase queer characters exactly? How does that help the plot?)
Sure i'll keep on watching but i'll come back to this question if it's not answered.
1. why does he not have Yeon Jun's memories like Jun Hee had for Min ju??
2. How can there be two of Si Heon exactly? I'd understand if the Siheon who was accidented in 2002 in a bus accident and now handicapped was actually in a coma up until the point Koo Yeon Jun dies in a plane crash in 2022 but that's not actually the case and Yeon Jun right now believes he is Si Heon and has only Si Heon's memories. He doesn't even remember loving Tae Ha until he got into an accident. (this part is pissing me off tbh. Why do we have to always erase queer characters exactly? How does that help the plot?)
Sure i'll keep on watching but i'll come back to this question if it's not answered.