Forum:Substitoad effect

can the substitoad not be destroyed by its own effect? And, why people use spirit reaper if the sssssssssssss substitoad (if it cannot be destroyed) is better? oh, and another question, can you activate the "once per turn" effects in your opponent's turn? oh, and another question more, can you activate the effects of goldd and sillva(dark world) with the effect of dark core/dark crusader?