Does calcium nitrate decahydrate dehydrate or decompose upon heating to 100 degrees Celsius?
Calcium nitrate exists under three forms : 1) $\ce{Ca(NO3)}_2 $ which melts at 361°C; 2) $\ce{Ca(NO3)}_2$$·\ 3 $$\ce{H_2O}$, which is not commercial and melts at 51°C ; 3) $\ce{Ca(NO3)}_2$$·\ 4 $$\ce{H_2O}$ which is commercially available and  melts at 43°C. It looses its water at 132°C and is deliquescent. The decahydrate that you mention does not exist.