Snapedom

1), Confundus does the same thing and is not illegal. Always assuming that a raging lunatic has enough cognitive reasoning in his brain for either to work. How often do we see a raging lunatic roaming the streets though? Anyway I don't believe in lunacy. I do believe in mental illness, but in my experience mentally ill people are usually more dangerous to themselves than other people and none of them have turned into raving madmen like we see in films and books. (I used to work in a hospital for the mentally ill.) As for pests, again it would depend on the circumstances. Rather than break the law I would rather use an exterminator. Or the WW world equivalent.

2) Using the AK as a means of painless execution of animals? I suppose it could be done. Seems like a large waste of power for something that there is already a system in place for. There has to be a system in place, the WW by and large is not vegetarian.

3) The problem about using Sectumsempra for surgery is threefold. The WW does not do surgery. They use spells and potions to cure what is wrong with the body.
It is very inaccurate and the cuts do not heal unless you know the counter spell and your patient could very well bleed to death while you are doing the unnecessary surgery if you don't get the counter spell out quick enough.

A surgeon has to learn on the job, so to speak. I don't think I would want to be the patient someone was practising on. And as for using it on animals. I'm not a fan of using animals as a method of experimentation.