I WROTE THIS REAL FAST LATE AT NIGHT SO IT'S PROBABLY QUITE WRONG OK?
tl;dr New glitch skips code at start of Chapter 2 and 3 which causes Louise in Chapter 2 and Lance in Chapter 3 to be skipped (as well as a few other missions) and almost all other missions becoming available at the start. This saves like an hour I guess.
1.0. What is the "Partial Act Change Bypass" glitch
2.0. How do you perform the glitch