why cant we continue the game endlessly as a normal sandbox game? why is there always a ending that gets the game over?
The game does enter Free Mode after February. There's only one real game over and that's from Dom Ava where she enslaves you and Dakota. If that's the MCSX you're getting, that's a choice you're making because other MCSX Endings are not like that.
If you're speaking about The Traitor, that's supposed to happen and it isn't a game over, just a cliffhanger.
How do you get Tasha's MSX endings? do I need her corruption at a certain amount before applying the MSX? What does the Change log mean by tasha being on her outgoing route?
You might need the MCSX Dose. You get it by:
Story: February after Chapter 4. Check Penny's Lab
Free Mode: Upgrade the Lab
After that it's mainly deciding what Direction you want to go in for Tasha
ANd Outgoing means you make Tasha start to embrace her sexulity which eventually ends with her dancing at the Strip Club