questions about the origin of singularity = nothing

Asking what is before the big bang only doesn't make sense in certain conceptions of the big bang, and using certain physics models. Interestingly, under both String Theory and Quantum Loop Gravity - which are, arguably, the two strongest contenders to replace Quantum Mechanics - the question can be asked, is meaningful, and can probably be answered.

No, it doesn't. That would be fallacy of composition (that a group will have the same properties as it components) - in other words just because everything in the universe has a cause and cannot create/destroy energy¹ would not imply that the universe itself has a cause or cannot have come from nothing (and vice-verse, doesn't imply it did either).¹ In fact neither of these things appear to be true, in QM things don't have causes and energy can be created and destroyed.