Why is the trackpad, keyboard, screen, and one usb port not working?

It sounds like your board has extensive damage on the board, did you spill any liquids on the laptop? The issues with the trackpad/keyboard are likely indicative of a cable issue or USB circuits, there is probably an issue with the IO board, the power rails to the battery are not working properly and if the fans are on full blast there is probably an issue with a thermal sensor. If it is liquid damaged, you may be able to recover some functionality by removing the motherboard and IO board, cleaning thoroughly with 99% isopropanol and drying it. Also check the IO board cable. If there are still persisting issues, then you will have to repair the motherboard or get it repaired.

I do believe it could be an issue with the Logic Board being that so many different things are being affected. If it were just the TrackPad and KeyBoard I would say perhaps a the IDP Cable which goes from your TrackPad to the Logic Board. But being you have so many other issues this fella up here saying Perhaps Liquid damage..?? Could be correct not saying you intentionally spilled liquid but it can happen heck I've seen a computer come in with Cat pee liquid damage and the customer had no idea. The only thing I would suggest doing if you open it up and it does show signs of Liquid would be to take it to the nearest Authorized Service Provider and have them look at it and perhaps give you a quote of a depot. Or you could send it off to a depot that we use called Micro Replay they will charge anywhere form $300-$650.. They will fix everything in the computer for you and they also give a year warranty on their work. Hope this helps in any way possible.