Are there any particular rules for this game as a run other than the ng+ thing?

Can I use CS clear data? Do I just use the final save time? Is the day 1 dlc allowed?

I've just transferred the rules over from the Cyber Sleuth for some consistency, dunno how they vanished here.

As for your questions: NG+ starts with the specific NG+ Option, by which you can transfer over anything from a formerly completed savefile. DLC is currently forbidden, but in NG+ it also wouldnt help you at all. Timing is done in real time, so either have a timer running or the length of the video.

Dlc is forbidden. Ohhh chapter 16 is not the right time to learn that