Now that photos can be used to get back to the past, this opens a lot of new speculation.
First of all, every photo that has been taken during the plot is now a point in time we could theoretically return to. The ones I remember are:
- The selfie during class
- Chloe dancing on her bed
- The butterfly
- The selfie in bed
Are there any more photos that have been taken in the plot? I can't quite remember because some of them (selfies in Max' room, all the trophy pictures) were optional.
Pretty sure that the selfie during class will be used to return to that time. It might even be what happened in Episode 1. This was a theory from the start, but I dismissed it because "Max can only rewind a few minutes or so". Well, the theory is now pretty damn possible.
TLDR: Episode 4 when?