Ineed to install a new toilet as the old i.e. had to be removed for new tilling and instead or using the cement product to hold the toilet in place can I use sikaflex as its holding strength is strong and the tiles are quite level

If you can't bolt down through the ring, drill through the tile and run a combo screw thread/machine bolt into the floor. Would the Sikaflex work? Probably but then you'd have another issue to remove the toilet if the wax ring leaked. Do it right.