No, you locked yourself from choices in THAT time loop... but all you needed to do is either go back a day (by asking CAS for partial reset) or ask CAS for full reset. Hell, there is even built in option to go back to earlier time slot within a day so you don't have to replay entire day to see different options. There is absolutely no hard lock of anything in this game! So there is no need to saving a lot or often... saving as you'd normally do with any other game is just fine.Actually, I have locked myself out of content. Last time through it was the hospital sections. Could only pick two choices out of three you were supposed to have as to whom for your mother to fire. Time before was something else. So, yeah, save at every decision. And that was with a step by step walkthrough. Couldn't go back because I didn't save earlier. Missed one thing, exactly one thing, and locked. Hard lock. So, save often, save a lot, and just save.
But your bigest mistake: blindly following step-by-step walktrough without paying attention to what is happening and what is said... that is an absolute recipe for disaster and getting lost in this game.