a. (-4,0) U [5,infinite)
b. (-infinite, -4) U (0,5]
c. [-4,0] U [ 5, infinite)
d. (-infinite, -1/3] U [ 1, infintie)
e. (-1/3, 1)

Answers :a.

No, but why get one if you won't use it?
Engineering requires blockage up to date with technology / advances, so if you're not in the industry, you will become 'out of date' which would accept implications if traveling for a job as a civilian engineer.

That said, alot of civilian engineering is about architecture principles, the fundamentals of those attempt don't change with time, although your anamnesis will.