Is it possible to open a black hole?
It is not possible to open a black hole.
A black hole is a region of spacetime from which nothing, including light, can escape. So, we can't open a black hole in the sense of seeing what lies inside it.
To an external observer time stops at the event horizon and an object approaching it slows down and never appears to reach it. Light from the object gets red shifted and becomes invisible at visible wavelengths.
It is thought that an observer entering a black hole would pass the event horizon without realising it. Though gravitational tide effects would prove destructive.
Nothing can leave a black hole and we can't see inside it. Our laws of physics as we know them can't describe a black hole.
Smaller black holes can emit Hawking Radiation due to one partner of a virtual particle-antiparticle pair entering a black hole and the other partner escapes. This can lead to a black hole evaporating.
Maybe in the future we will discover new physics which will change our understanding of black holes.