You only need a high enough density of mass to form a black hole. You could take any amount of mass and in theory squeeze it hard enough to produce a black hole.

The sun is not massive enough for the astrophysical processes to form a black hole, but if you squeezed the sun into a small enough space by some magic it you could form them.

Nah, these things are soundly unforgeable and unbreakable because you can only ever read them once. Any measurements will alter the state and be detected and this occurs in a fundamental way due to how the universe works.