would you please revise my writing ??

1. South korea goverment had made an experiment in Nuclear weapon from 1970 to 1980's 
 

The South Korean government performed (or conducted) nuclear experiments in the 1970's and 80's. (this is what I would say if they did multiple experiments during this time)

Would you please revise my writing?

1. The South Korean government had made an experiment in nuclear weaponry from 1970 to the 1980s.


2. Korean men have to participate in the reserve forces for a total of 8 years after finishing their regular army service which lasts for about 2 years.

3. He has been objecting to the new policy of producing products which employees made before.

There you go~ ㅋㅋ