This is an explanation of the loophole (for any of those who don't understand), my theory, and I think a few "whoops" moments I found.
Season 4 Finale: (Late December 2004, Early January 2005): Ben turns the wheel, the island moves, Locke goes through his first time flash. *The Other's saw the bright light too*
Season 5, Episode 1-5: Locke goes through another time flash, sees the Nigerian Plane crash, gets shot in the leg by Ethan, and goes through another time flash. *By this time I think it must be October 2004, since Ethan is alive and the Nigerian Plane just crashed*
Locke stumbles to the fallen Nigerian Plane, just as Richard walks out of the jungle. He tells Locke he has to bring The Oceanic 6 back, and to do that he has to die. He gives Locke a compass and tells him to give it to Richard when they next meet. Locke goes through another time flash. *Richard did not notice the bright light*
Locke joins up with the other main characters, goes through some time flashes, and gets caught by The Others. While there Daniel tells them they have to bury the leaking hydrogen bomb Jughead underground, so they won't get radiation poisoning. Locke gievs Richard his compass, and tells him he's there leader. He asks him how to get off the island. Richard doesn't tell him. They go through another time flash. *The Other's didn't notice the bright light*
Locke tells Sawyer he think he knows how to stop the time flashes. He says they have to go to the Orchid. On the way there they go through more time flashes, and Charlotte dies from them. With Daniel with Charlotte; Sawyer, Locke, Juliet, Jin, and Miles head to The Orchid...only the elevator to get down is gone. Instead they find a well going down. As Locke descends down the well, another time flash comes and he falls, getting a sharp piece of something in his leg. The well dissapeared, and they couldn't help him. Sawyer, Jin, Miles, and Juliet all look up to see the back of a statue.
Down in the Orchid Christian* appears, *Now this is very important so I'm putting a * beside his name*, saying he's going to help him. He tells Locke there's a wheel here off it's axis, and all he has to do is turn it. Locke does, and teleports off the island. The rest of the survivors go through one last, big, green flash...and it ends. They are now stuck in 1974, and Locke is off the island.
Season 5, Episode 7-16: Off the island, Locke wakes up in the Tunisian desert, but unable to walk after getting jabbed in the leg with a sharp object. Later that night a pickup truck comes after seeing him on a camera. They bring him to a nearby medical centre and painfully take the object out. Charles Widmore visits him, and gives him a new passport, his new name being Jeremy Bentham. For the next 3 years Locke tried to convince the Oceanic 6 to return, but failed. In his hotel room, Locke wrote a note to Jack saying "I wish you had believed me." *I think it was referring to them having to go back, or him telling Jack they weren't supposed to leave.*
Locke wraps a wire into the ceiling, and is just about to hang himself when Ben comes in. He tells John he's very important, and asks how it went, convincing them to come back. John says he failed. Ben takes Jin's ring from him, and helps him into his wheelchair. He tells Locke he didn't fail. Last night Jack bought a plane ticket from L.A. to Australia, and if he has Jack he can get the rest of them. Then, he strangles Locke.
Jack, Sun, and Ben follow Eloise's instructions in episode 6, and try to reinact the original plane crash. They put Jack's dad's shoes on Locke, and put his body on the plane. Also on the plane was: Sayid; arrested for killing a family member when he was a hitman for Ben...Hurley: Jacob told him the flight number and time and gave him a guitar case...Kate: returning to find Claire. As 5 of The Oceanic 6 and Locke's body go on the plane, Jack reads Locke's note to him. There's a bright flash, and Jack, Kate, and Hurley teleport to 1977, where Sawyer, Jin, Juliet, Miles, and Daniel are now. The Ajira plane goes through the window, and lands on a runway on the Hydra. Locke* is apparently resurrected.
Locke and Ben go to the main island, to find Sun and Lapidus there in the Dharama barracks. Ben has come back to get judged by the smoke monster*, but has lost the ability to summon it. Locke and Ben to to The Temple, and go down one of the holes. *Now, this is the first out of 2 loopholes, so i will use *** to show where it is*
- Ben falls down onto another floor of The Temple, and Locke* goes to look for some rope to get him out. Ben looks at some hieroglyphics and a bunch of small holes on the ground. The smoke monster comes out and judges him for letting Alex die. It disappeared, when suddenly Alex* was behind him. She told him he has to do everything Locke* says or she'll destroy him. Locke shows up at the hole and said he found some rope.***
Lapidus goes back to The Hydra, only to get asked by Ilana and Bram What lies in the shadow of the statue *I think it's a security question*. They knock Lapidus out, take a crate, and move on with some members of Ajira.
Locke*, Ben, and Sun join up with The Others, and Locke* resumes his leadership duty with them. *It's present time, 2007, right now too* Locke*, Ben, and Richard go into the jungle to the Nigerian Plane. Locke* tells Richard a man is about to stumble out of that jungle. He tells Richard to tell the man he has to bring everyone back to the island, and to do that he has to die. He also gave Richard a compass to give to the man, to give back to Richard. The man is Locke*
That's the two loophole's. Season 5 Finale Opening Scene: The man in black has to find a loophole to kill Jacob, and this is what happened. Mostly everyone's theory, and mine (it's probably right too) is that the man in black is the smoke monster, or controls it. That means after the Ajira flight, it wasn't Locke, it was the smoke monster, because in the crate that Ilana had, was Locke's body. So, in the first loophole, Alex* (* means smoke monster) told Ben to follow Locke*: that means Ben would be following the smoke monster, thus having to kill Jacob without a choice because Locke* told him too.
The second loophole, Locke* made sure Richard told Locke he ahd to die, thus putting Locke in an loop where he always died, so Locke* could take over his body.
Doing this, he could kill Jacob, because he can't kill Jacob without using a loophole.
Whoops moments: 1: In the season 4 finale the Others saw the light, but all during Season 5 they didn't. 2: It was about 2004 originally when Richard told Locke he had to die...but when Locke* told Richard to tell Locke that, it was 2007...so either I'm wrong or they accidentally made a 3 year time gap.
Sorry it was so long, but I needed to do that :)