I want to make 14 mm resin cabochons, but all I can find are molds for CLAY 14 mm cabochons. Can I still make resin jewelry from that kind of mold?
It's not going to give you complete coverage of the matteressbut there's no reason why you can't put the topper on the XL mattress.
If you are only installing one unit then you can simply leave the red wire disconnected. Though cover the end of it with a screw on connector or electrical tape so it doesn't accidently make a connection. The green wire is the earth wire, if there is no green wire or the instructions do not mention earthing or grounding the detector the you can leave this one disconnected also. Smoke detectors save lives, so I commend you for installing/replacing yours.
I believe the red wire is to connect several detectors together, so when one is set off by smoke, the others go off at the same time. I am not positive about this..