I wanted to quickly address the medical euthanasia aspect. Yes it exists. I had a Brazilian Rainbow Boa that I rescued and over a few years it never did get better. Turns out it had been starved for a long time and kept without water. It was tested for everything possible, all negative. In the end, the conclusion was that it suffered from irreversible kidney damage from the neglect. Whether this is true or not, it just wasn't getting better. I took it to the vet and had it medically euthanized. I was there when it was given the injection and held it until it died in less than 2 minutes. The vet checked for a heartbeat to insure it wasn't still alive. So yes, it is possible.