It is acceptable to spell "nonviolence" both with and without a hyphen.
Without a hyphen
That is correct. It may also be spelled without the hyphen
hyphen
You can spell reuniting with or without a hyphen. Since the mid 1990's the Oxford English Dictionary has encouraged writing words without hyphens wherever that can be done without obscuring either the meaning or the pronunciation. Reuniting is probably better without a hyphen.
It used to be that a hyphen was used in prefix words. Now it is without hyphen. He wanted to reestablish control.
no
The phrase is spelt "ten-pin Bowling" - sometimes to be found with the hyphen, and sometimes without.
The phrase is spelt "ten-pin bowling" - sometimes to be found with the hyphen, and sometimes without.
good bye good-bye goodbye (this is the right way)
Some dictionaries list it without a hyphen, as "housesit" (and housesitter, akin to babysitter). This is likely a case of evolving usage. Many spell checkers will only accept the two-word form.
When it's used as a verb, spell it as follow up (no hyphen). When it's used as a noun or adjective, there is a hyphen (follow-up). Go to dictionary.com. In the Dictionary tab, type in the words 'follow up' without the hyphen. This will help you a lot.