Let's see if I can get this straight. This is the order it happens in, as I understand it:
Veronica and Lily are the same age, but she is in the class with Duncan and Logan and Lilly is in the class ahead, so the homecoming dance is Veronica, Duncan, Logan's Freshman Year and Lilly's sophomore year.
The next year Veronica returns to school and Duncan doesn't acknowledge her, Celeste has told him that they are sisters. Lilly tells her Duncan is weird, or something like it. Veronica is hurt. she is still Lilly's friend and hangs out with her. Veronica meets a new friend who kisses Logan, who Logan kisses knowing it will get back to Lilly and break them up, but Veronica self righteously takes this upon herself and loses a friend and learns not to follow orders from Lilly, anyway it is a meaningful experience for her.
At the car wash Lilly tells Veronica she has a good secret, although she has many this is almost certainly having sex with Aaron, which Lilly would find gossip worthy, It is uncertain if this is an ongoing affair, she may be going to meet him to have sex for the first time after the car wash.. Anyway, Lilly is then killed.
Duncan's parents, assuming he is the killer, take him out of the picture, medicate him and hospitalize him, he is not available to Veronica or Logan as a friend.
Keith loses his job, probably by Christmas. Lianne leaves. Keith starts PI business.
Veronica helps him sell stuff, maybe sell house, find apartment, find place of business, does receptionist duties, starts doing surveillance, working a couple full time jobs and going to school.
This means Logan is abandoned, takes it out on Veronica in the spring, bullies and ostracizes her. Tells people she has 'chosen her father over her friends'.
She starts to toughen up, while learning the PI business.
At the end of the school year party that Shelley holds Veronica decides to give the group of 09ers a fuck you and goes to the party, but does something stupid, takes a drink from an enemy (I suspect Madison and Veronica have bad blood all along, but we never learn the details), and eventually is sexually assaulted by Logan and then raped by Cassidy and Duncan. She goes to the paternalistic (her Dad was sheriff) institution for help, Lamb the current Sheriff tells her to go see the wizard. She realizes if she now goes to her Dad he will lose it, beat up Lamb and be arrested, she can't tell him. She sees the Wizard, decides to be the person who helps the people paternalistic society will not help. Cuts hair, changes style. Continues to work as a PI, doing actual cases.
The next fall goes to school, her junior year, cuts Wallace off flagpole.
And we are off!
Thank you for that pre-show timeline. I've never seen it laid out like that, and it's really helpful.