one of my favourite spins on Stab-is-the-Scream-inside-Scream is in Detention (2011)

when the protags realise they're being hunted by someone acting out a film, they download the trailer for the latest release in the franchise, which shows its protags doing the same, and again, and again...

each nested version becomes a cheaper knock-off with the final being a video nasty starring Ron Jeremy