No for a Very good people.
Yes for a normal people.
I would assume so unless you had a license or if the thing was trying to kill you which would be a valid reason to kill it without a license.
When there is good reason you did not do your homework you have a valid excuse.
No, you cannot trespass someone without a valid reason.
No, a teacher cannot fail a student without providing a valid reason.
Well, yes. Whether it's a valid one depends on what your situation is. For example, it's a valid reason not to watch TV, but not a very valid one to skip school.
No it's not as the management need to have a valid reason and if they don't have a valid reason they can't refuse you entry.
No and there is no valid reason to.
No, police officers do not have the authority to exceed the speed limit without a valid reason.
If you have a valid reason, certainly.
It is valid but it is reserved as a source address only by RFC1700 standard.
If the reason is valid, yes there are
There are cases where believers of ANY religion have a perfectly valid reason and both the right and duty to kill another human being. Different religions set different boundaries on this and some people deliberately misinterpret what their religion says on this matter for their own reasons having nothing to do with the religion that they claim to believe or represent.