Good News and Terrible News!
The Good News is that I've beaten the Flashback scenario (since I don't want to die, I got the "Leaving the Mystery Behind" ending.) and got the fifth scenario.
The Bad News... Everything went very wrong on the fifth scenario:
Cindy died. (Because of her virus gauge and that sniper.)
I tried to get the "Up and Away With Linda" ending, but unfortunately, I didn't make it because of the Tyrant and I don't know which way to go.
I died immediately afterwards.
Thank goodness I don't have to fight the final boss. It will be much worse!!