simultaneously concurrently
The word is contemporary.
simultaneously
There is no short word for "simultaneously", but the word can be expressed as the phrase "at the same time" or "as one."
Once
There are a few one word that mean the same thing as called off. You can used the word quit, out or time.
Happening one time and since the word once is almost like one. One and once almost have the same meaning that will also help you.
Yes, that is one meaning of the word "exact" (precise, accurate). If you are using the phrase, however, it may use the adverb : "at the exact time" but "at exactly the same time".
punctual
Having two wives at one time is "bigamy" (illegal in the US, but common in some societies). The general word for having more than one wife is polygamy.
People of the same time period are referred to as contemporaries.
No -- one is an adjective and one is an adverb. Their forms are based on the same word, though.
yes