Um, wow. you are very, very far behind. The show has become a different show twice since Season 3. (Seasons 1-4, 5-7, 8-10 are pretty different.) Very little of the show is the same, other than the premise of seeing Superman’s life before he was Superman.
Basically forget what you know. Clark is now almost Superman, currently being a costumed vigilante called The (Red and Blue) Blur. He has a bunch of superfriends, his cousin Kara (Supergirl) and Oliver Queen (retired Green Arrow) being the main ones.
Lois made it to Smallville early on, and Lana is finally history due to a plot contrivance. Lois and Clark both live in Metropolis now (where Clark can be a better hero), and are engaged. She has replaced Chloe as the reporter, while Chloe moved on to sidekick status, helping out the Justice League (the superfriends mentioned above), and, like everyone in this paragraph, knows Clark’s secret.
Lex is dead. Or, at least, that’s what he wants us to think. Currently alive is a clone of both him and Clark named Connor Kent, who is currently a good guy. Lex had went entirely evil before he was killed, and knew Clark’s secret. His father Lionel is dead, but a version from an alternate reality is back. He is currently plotting with a new villain called Darthseid, who is semi-corporeal shapeshifter who can possess the non-innocent. He feeds on fear and hate, and is trying to possess Clark to become all-powerful.
There’s a costumed vigilante registration act that was recently a big deal, but is now defunct. Clark and the JLA were all technically fugitives, other than Oliver who acquiesced. This was all led by a guy who Darthseid possessed. The act was defeated with help of Senator Martha Kent who took the job when Jonathan died (a death Clark blames himself for).
Lex was originally replaced by Tess Mercer, who is now a main character, but, like Connor, has also reformed to being good (we think). Lex, when just missing, tried to control her, but she broke free and has been helping Clark most of the time. She was raised back to life by Darthseid, and, while still trying to be good, is supposed to be his servant. We don’t know how that will play out.
The big things everyone expects to happen in the finale is that Clark finally can handle flying on his own, not in a virtual reality, and not as a different person using his body. We also expect him to wear the suit, which he has already seen, but it was taken by the AI copy of Jor-El that lives in the Fortress of Solitude, and is being held until Clark proves he can handle it. (Jor-El also told him when he took it that he will never become the Earth’s greatest hero, but we’re not sure what that means.) We hope that the original Lex may show up, as the actor has not confirmed nor denied his involvement, having left in season 7 after his contract was up.
And that’s all I can think of at the moment. My sister’s the real fan, and I should be seeing her some time today or tomorrow, so I’ll ask her for more information.