I know I have missed things (I didn't realize before that there were hidden things in the flashbacks and also didn't realize that after you talked to someone you couldn't go back. I am curious if before the end of the game you can go back to redo things to get everything? And if you get everything, is there bonuses or anything?

At the main menu you can choose Play Episode and choose what episode you want to play over. The only unlockable bonuses in the game is concept art.

This will add to what you play though, right? I mean you don't have to continue to play from that point? Because there aren't multiple save options.

I believe if you have missed an item in a previous episode you will have an opportunity to pick one up before you actually need it.

Sorry these are in the flashback memories I meant.