You got good responses to the rest but

> The adults around me couldn't explain scientifically what the actual difference was between a CZ and natural diamond.

I was told growing up you can just check with window glass. If the gem scratches it's CZ and if the glass scratches it's diamond.

CZ is very cheap costume jewelry and won't last as it scratches and dulls so easily

I remember watching a documentary about a man who would marry (multiple) women, then steal their money and leave.

one of the victims said she had doubted the ring he gave her was real, but he just scratched a mirror with it to prove it was real. Then she said "it was only later after he left that I found cz can also scratch glass"