The only wat to tell if you have any CC is to use a DPD test or an FAS-DPD titration test.

The way CYA works is that it combines with the chlorine to form cloroisocyanurates in the water. These will test as FC but they do not have the oxidizing power of hypochlorous acid.. This combining is not complete if the CYA and FC levels are kept in the recommended ranges so there is some FC available. When the CYA is too high then most of the FC is combined unless you raise the level with unstabilized chlorine. (This is an oversimplification but it gives you the idea.) CYA has no effect on an OTO, DPD, or FAS-DPD test since the combined chlorine it produces will test as FC on DPD and FAS-DPD and as part of the TC on an OTO test.