Ctrl Alt Del

Well the time travel, hrmmm, well you can travel through time from any save point, but can only go to specific "nodes" which are deemed important. If you are just pushing through the main story it will be pretty obvious when you need to go back in time, the side quests are a lot more subtle though. I really have to hand it to the writers though, I don't know how they managed to write the story with no plot holes, at least none major or minor that I've seen. You'll be presented with several choices and sometimes if you pick the "wrong" choice you'll actually just see a blurb about what happens before being forced back in time to choose the other option. So yeah, that's kinda how you make use of time travel, sometimes you need to go back to make a different choice, and sometimes you need to go back to grab an item you need later but didn't know about.