My Object is duplicated more than once Once Tapped On Screen!

Hi everyone,

I have been started working on vuforia fairly new. Now I can manage to create my 3d object on any surface when tapped on Ground Plane Target. But however whenever I tap it like duplicates the same object more than once. And Also I when I tap other parts of my living room it continues to get cloned almost. Is there a way to fix this and always create only one object once tapped on target and if create then maybe delete the last one vice verca! Also the script called DeplyStageOnce seems not working. And even tough I tick the duplicate stage off, it still duplicates the objects.

I would appreciate help on this. 

Thank you!