Yup, Propad can be used for doors. 4 doors you will need 4 boxes.... Normally I only suggest 1 box per door, but if you decide other wise, then it is entirely up to you.

Propad = SuperLon ??? 

No la, bro. Propad ~ Suppression Pad, only using bitumen as the adhesive layer.

SuperLon = Insulflex, they are brother and sister until someone start fighting and the company split into half.... That's what people told me la. 

Alumimium sticker???    What aluminium sticker? You mean the layer ah?

Your door panel = door metal body, right?

Normally I refer door panel as door trim, the layer of your car door that made of plastic.

No la, Propad is not sponge... Some plastic la.. 

Yes, the Propad is meant for door metal part. Can withstand heat, and definitely will no melt under normal circumstances.

1 box per door, 4 boxes for 4 doors. Easy application with great effects.