rockerface🇺🇦

Just getting lucky, then

how did they even prevented infection/allergies

Well, they either got lucky or died. But also, alcohol probably already existed at the time.

Exchanging germs to synchronize antivirus databases

Not bonds within atoms, bonds between atoms. Or molecules. That depends on the exact material being cut.

And yeah, on a large scale it gets exploded, but on a scale of cutting paper with scissors it mostly gets lost as heat.

But also, because some of the bonds between atoms/molecules were broken, some of the energy was lost. And energy is mass, so you can lose mass even if all the particles are still on either piece.