"What are the reasons behind the difference in 1st, 2nd and 4th Amendment Rights. Explain them one at a time, please."
Our 1st Amendment right is limited in order to maintain discipline and not foster insubordination. Speaking out against your leadership can be punished by up to 9 months confinement.
The 2nd Amendment right doesn't exist if you live in the barracks. All firearms must be registered within 72 hours of being bought, or after moving to post and they must be stored in the unit's arms room. If you live on post housing, you may keep your firearms, but they still must be registered. If you live off post (thanks to that A-hole in FT Hood), your weapons still need to be registered on post and your command may come to your home to inspect them.
The 4th Amendment right does not exist on post. The Commander can direct searches of your vehicle, barracks or quarters at any time without a warrant, this includes having the dogs go through your living area. The command may conduct a "health and welfare" check of your residence off post as well.
Fear the man who has one gun, for he knows how to use it.