Start: Quirrellmort is trapped in the reflected portion of Hogwarts; Harry is under the cloak and thus not reflected, but still trapped in Quirrelmort’s ring; Dumbledore is on the other side of the mirror, unrestrained AFAIK.
Dumbledore starts the time-freeze on the Hogwarts side; Quirrellmort reveals Harry, takes the cloak and puts it on himself so he then doesn’t have a reflection, and steps out of the reflected portion of Hogwarts.
Dumbledore reverses the time-freeze to act on his side to protect Harry. Dumbledore then disappears from the mirror.
End: Quirrellmort is free to roam about the physical world and has the cloak; Harry is still presumably trapped in the reflected portion of Hogwarts, but he is safe from the time-freeze; Dumbledore is frozen somewhere, but the Elder Wand and the Line of Merlin Unbroken have been left unfrozen as he cast them aside right before he disappeared; they are possibly now in the physical world with Harry and Quirrellmort.
My understanding:
Start: Quirrellmort is trapped in the reflected portion of Hogwarts; Harry is under the cloak and thus not reflected, but still trapped in Quirrelmort’s ring; Dumbledore is on the other side of the mirror, unrestrained AFAIK.
Dumbledore starts the time-freeze on the Hogwarts side; Quirrellmort reveals Harry, takes the cloak and puts it on himself so he then doesn’t have a reflection, and steps out of the reflected portion of Hogwarts.
Dumbledore reverses the time-freeze to act on his side to protect Harry. Dumbledore then disappears from the mirror.
End: Quirrellmort is free to roam about the physical world and has the cloak; Harry is still presumably trapped in the reflected portion of Hogwarts, but he is safe from the time-freeze; Dumbledore is frozen somewhere, but the Elder Wand and the Line of Merlin Unbroken have been left unfrozen as he cast them aside right before he disappeared; they are possibly now in the physical world with Harry and Quirrellmort.
[edited iteratively]