Ok i have made an easymode mod for people to use on Stats, and in there the only option i've highlighted is the Mercedes locking off the Shelby path.
Easymode will let you start with 100 of each of the girls stat if you select that from Chapter 1, or add 100 of each girls stat if you select it from your existing save. I would suggest if you havent seen all scenes that you start from the beginning though.
The only options i am highlighting are the ones that block off other paths as the dev makes it clear when the current girl's path is closing.
I have test this with the old saves as well and if easymode is not activated then it will prompt at the start of each chapter (without having to start a new game). But if you missed any scenes i would start at the beginning.
Let me know if there are any issues.
Instructions: copy and overwrite the files in the game folder.