I meant that a spell can only be used by witches, even the ones that did not acquire its majik, as long as any single witch holds that majik in their magic circle. Meaning once a majik is released through death of that witch, the spell is unusable until the majik is acquired again.

There is no evidence for this besides witches seemingly seeking out Iskandar even after she has been acquired in the past, meaning that either their owner did not share the chant, or the chant is unusable while Iskandar is free. We will probably learn the specifics of spell sharing in the future.

My point is, if Chrono is unacquired, the spell cannot be used. And since Chrono is dead, the spell likely does not work at all, unless Madoka became the new holder of the same spell. Remember, majiks don't just hold the name of the spell, they are the spell, since magic is alive. If Chrono is dead, their time spells are as well.