Oh c'mon, who's going to send an own agent to a place where you know four terrorists are going on a rampage with automatic rifles and grenades?
Russia would, and they weren't sent there, the agents were already there before they arrived (assuming there was more than one). Risk can be reduced by instructing them to:
1) Make entry through the parking lot (see animation in post
#12);
2) Do not split;
3) Head to the theater's main entrance;
4) Engage people along the way;
5) Do not engage the balcony area;
6) Start a fire in the theatre;
7) Leave the theatre through the same path;
8) Leave the building through the parking lot.
With the instructions above, all the agents needed to do was to remain in the theatre, in the balcony area, and wait for their arrival and exit of the terrorists.
With the 'operation' being a mass shooting, what does that even mean?
That would be the means for the goals, not the goal itself. It would be the goal for ISIS, whatever that means for ISIS (their relationship with ISIS is still not conclusively established, by the way).
Crocus could have been 1) an ISIS terrorist attack, or 2) a Russian false flag, or 3) an attack using ISIS operatives but masterminded or abetted by Ukraine.
So far, no one tried to make a case for 3, hence my post stating there are only two hypotheses in this thread.
because Putin does not need a false flag to escalate in Ukraine if he wants (or if he could)
The false flag can be used for justification of escalation, Putin speaks to his internal audience as much as the external. I can think of several reasons where he would try to make the most out of a false flag in relation to Ukraine, but I also do not think that was his main goal under hypothesis (2).
ISIS has taken credit for the attack and published videos which confirm they were the culprits.
No, the news agency historically associated with ISIS published a text that looked suspicious. Then a photo was published with blurred faces and masks, the only relation with the photo and the suspects is the clothing. Then the footage appeared. Was it a live stream? Was it sent to ISIS during their escape? Was it taken directly from their phone after capture? Still, ISIS could have used them, the secret services took notice (the Western services certainly did), and the FSB decided to let them do it by creating the necessary conditions and shaping the plan (2a). Or there was never any ISIS, only the FSB (2b).
The evidence we have for 1) is high: ISIS has taken credit for the attack and published videos which confirm they were the culprits. Evidence for 2), the false flag, is zero
It depends on how you define "evidence", certainly there is suspicion, and the absence of evidence is not evidence of absence.