i) A person shall tried in a military tribunal when the person is a member of army or in the military. There are rare cases of civilians being tried in the military tribunal.
ii) it was very constitutional to have tried southern-sympathizers involved in John Wilkes Booth's plot on President Lincoln and other high government officials, even if at the initial it wasn't, but steps were taken to make it constitutional
iii) No, it doesn't matter whether the plotters had connections with the Confederate Secret Service.
iv) Three hundred Dakota warriors sentenced to death in 1862 by a military tribunal for their role in an uprising against Minnesota settlers was constitutional as they hampered their wellbeing.
v) Since the individual isn't an American citizen then the constitution provides that such person can be tried in the military tribunal but if the offender is an American citizen the civilian court will be used. The constitution says the terrorist who aren't American citizen should be tried in the military tribunal.