Most of the Japanese made guns will interchange without fitting. On Belgian models, it is recommended that a qualified Gunsmith fit the barrel for you. Fitting is simply "the fine grinding of the metal" to make the barrel recoil back into the receiver smoothly.
No
No
Check the barrel and receiver.
if the gauge and chamber length are the same
Library.
No it will not.
Follow the instructions in the A5 manual using the link below.
Where will be marked on the barrel or receiver. When is 1977.
No, the Ion and A5 have different threads.
No
No
No