Both
onetime means occurring only once, or formerly, depending on usage as adjective or adverb.
one time; as to have a turn only once.
Forty one is the correct spelling.
The correct spelling of 41 is "forty-one."
That is the correct spelling of "recipient" (one who has received something).
That is the correct spelling of the word "multiple" (more than one, or a higher number).The correct spelling is multiple (more than one, many).
It is one word, not two. The correct spelling is goodbye.
There is only one i in it, which is at the end. So the correct spelling is Alumni.
That is the correct spelling of "quicker" (faster).
That is the correct spelling of "communication" (exchanging info or ideas).
The one you used is correct.
The correct spelling is bestiality. It is one of the most commonly misspelled words.
The correct spelling is all one word, crossover.
The correct spelling is athlete (one who engages in sports or gymnastics).