Why can you use Panoptic Mirror first ability in response of the upkeep triger to remove a sorcery or instant and you already can use it?
I have this question because when you useJhoira of the Ghitu ability to suspend a card in response to your upkeep triger, you can not remove a time counter until your next turn.
Panoptic Mirror's second ability cares what cards are exiled with Panoptic Mirror when that ability resolves, and not when it triggers at the beginning of "your upkeep" (C.R. 608.2g, 603.2). Thus, it can count such a card even if it was exiled after that ability triggered and before it resolved (C.R. 607.2a).
On the other hand, suspend means, in relevant part, "At the beginning of your upkeep, if this card is suspended, remove a time counter from it", which necessarily follows that the card has to be suspended, that is, "[be] in the exile zone, ha[ve] suspend, and ha[ve] a time counter on it", at the beginning of "your upkeep" for that part to trigger, due to the intervening "if" clause (C.R. 702.61a-b, 603.4; see also C.R. 113.6b). If cards are exiled due to Jhoira during that upkeep, the second part of the suspend ability they would gain due to Jhoira won't trigger during that upkeep (review C.R. 702.61a). See also this thread and this thread.
I have this question because when you useJhoira of the Ghitu ability to suspend a card in response to your upkeep triger, you can not remove a time counter until your next turn.
On the other hand, suspend means, in relevant part, "At the beginning of your upkeep, if this card is suspended, remove a time counter from it", which necessarily follows that the card has to be suspended, that is, "[be] in the exile zone, ha[ve] suspend, and ha[ve] a time counter on it", at the beginning of "your upkeep" for that part to trigger, due to the intervening "if" clause (C.R. 702.61a-b, 603.4; see also C.R. 113.6b). If cards are exiled due to Jhoira during that upkeep, the second part of the suspend ability they would gain due to Jhoira won't trigger during that upkeep (review C.R. 702.61a). See also this thread and this thread.
EDIT (Aug. 31): Correctness edit.