BTTF Timeline Breakdown

Twin Pine Timeline

This is the timeline we see at the beginning of Part I. George and Lorraine are together, but their relationship is strained. Biff is George's supervisor at work and continues to bully him. Lorraine is an alcoholic and disapproves of Marty's relationship with Jennifer. Dave works at Burger King and presumably still lives at home. Linda seems to also live at home, but there isn't much detail about her personal life. Marty has no truck.

Lone Pine Timeline (Clayton Ravine)

This is the timeline we see at the end of Part I and the beginning of Part II. George and Lorraine are together, and their relationship is healthy and full of love. George is a successful author who published his first novel in October 1985 and drives a BMW. Lorraine is sober and is supportive of Marty and Jennifer's relationship. Dave has a nice office job. Linda seems to be more successful than her TP counterpart, but it isn't made explicit. It is unclear if Dave and Linda still live at home. Marty has his truck. Biff is no longer an office supervisor and now owns an auto detailing business. He's much more timid around George now.
    Marty gets into a traffic collision with a Rolls Royce and injured his hand to a degree where he couldn't play guitar again. In 2015, Marty has a dull office job at CusCo and a failing relationship with Jennifer. On October 21, 2015, Marty involves himself with unspecified illegal activity and is fired over it. Marty Jr. gets involved with Griff's gang and is incarcerated for a bank robbery. One week later, Marlene is incarcerated for attempting to break her brother out of jail.

Hell Valley Timeline

This is the timeline we see in the middle of Part II. On November 12, 1955, Biff is visited by his older self and given the Gray's Sports Almanac. Biff uses this to cheat at gambling and create a billion dollar empire. On March 15, 1973, Biff murders George. At some point after this date, Biff marries Lorraine. By October 22, 1985, Dave is on parole, Linda is in immense credit card debt (that Biff pays off), and Marty is supposed to be in a Swiss boarding school. Doc has been committed to a mental hospital. Sometime in the 90s, Lorraine shoots Biff as explained by Bob Gale.

Lone Pine Timeline (Eastwood Ravine)

This is the timeline we see at the end of Part III and the beginning of Episode 1 of BTTF: The Game. On September 4, 1885, Clara arrives in Hill Valley. A snake spooks her horses, and she is saved from death by Doc. On September 5, 1885, Marty with the pseudonym of Clint Eastwood saves Doc from being shot by Buford at the town party. He's challenged to a duel on September 7 at 8:00AM.
    Marty manages to win the duel without firing a shot and still giving him and Doc plenty of time to catch the train to push the DeLorean to 88mph and take them home. While Doc is climbing to join Marty in the DeLorean, he sees that Clara followed them out there. Through a matter of circumstance, Doc and Clara stay behind in 1885 while Marty returns to 1985. Presumably, Doc and Clara explained to the rest of the town that "Clint Eastwood" died in the ravine.
    In 1985, Marty backs out of the street race with Needles. He never gets into a wreck with the Rolls Royce, meaning he never broke his hand, meaning he never gave up on his music. The only thing that's now certain about his future is that he never gets fired from CusCo presumably because he'll never work there in the first place.
    By May of 1986, Doc hasn't been in Hill Valley since October of 1985 and is assumed dead, causing the bank to hold an estate sale.

Tannen Mafia Timeline

This is the timeline we see near the beginning of Episode 2 of BTTF: The Game. On June 13, 1931, Arthur McFly was served a subpoena and testified in court about the crimes of Kid Tannen and his gang. To avoid being killed, Arthur leaves Hill Valley that night, but sticks around close enough to marry Marty's grandmother and keep that part of the timeline intact.
    However, because of this, Arthur isn't there to check Trixie's work, and Kid never gets convicted of federal tax evasion. In 1955, George still stands up to Biff at the dance, but that makes him a prime target for the Tannens' abuse, In 1986, the Tannens are now the fifth most dangerous crime family in California. Dave, Linda, and Marty have all left town. Marty specifically left town so that the Tannens wouldn't be so hard on George.

Citizen Brown Timeline

This is the timeline we see at the very end of Episode 2, the entirety of Episode 3, and the beginning of Episode 4 of BTTF: The Game. On August 25, 1931, Emmett is involved with the arrest of Kid Tannen and catches the eye of Edna Strickland. Through her influence, Emmett's path of science veers from inventing to be more psychologically based. He gets into politics and is eventually elected mayor and (with Edna as the power behind the throne) turns Hill Valley into a police state.
    George and Lorraine's relationship is back to being unstable. George essentially gets paid to be a peeping Tom. Lorraine is an alcoholic again. Dave and Linda left town. Marty is a straight-A model citizen. Jennifer is a punk anarchist. Biff initially remained unchanged from his TP counterpart, but was brainwashed to be completely docile.

Arson Timeline

This is the timeline we see briefly near the end of Episode 5 of BTTF: The Game. On October 13, 1931 Edna gets her hands on the DeLorean and winds up in 1876 where she burns down the saloon in an act of fury. Since the surrounding buildings were all made of wood, the fire spread and all of Hill Valley was burned down. Seamus and Maggie settle in Hayesville instead of where Hill Valley used to be. Not much else is known about this timeline.

"This is Fine" Timeline

(name subject to change)

This is the timeline we see at the very end of Episode 5 of BTTF: The Game. Emmett and his father Erhardt reconcile at the Hill Valley Expo, and Erhardt supports Emmett's passion for science even if he doesn't understand it. The Browns have a residence in 1986 now and instead of an estate sale, they're simply having a yard sale at Doc's lab. At some point, Doc is awarded the key to the city for unspecified reasons. On an unknown date, Kid marries Edna and she becomes Biff's step-mother.
    Some unspecified timestream conundrum happens far in the future which causes three different versions of Marty to come back to May 15, 1986 to sort things out. Instead, present Marty and Doc decide to leave and figure things out on their own.