Answers for question 4 and 5

4. How would it be possible to own a gun?
5. How strict are the guns controled by the governments?
Not everyone can hold a gun, and that comes in common for every country. Typically, you must pass a certain test, where you are above age (differs dependng on countries), has no crime records, has no mental issues, is not addicted to drugs and alcohols, and is a citizen of the counrty you are trying to hold a gun in. You would also need a propor reason and knowledge to own a gun so you must get a licence before purchacing a gun.

As you can see from above, usually you must go through a strict check to own a gun, but also mentioned in the answer from question 3, America has many loop-holes in their laws. The strictness may differ in countries.
In Japan, guns are strictly controled by the government. There are many checks to purchase a gun, and after that, you must report every single reason for the shots.