o'er vs over

o'er is not a noun while over is a noun.

Word	Noun	Adjective	Verb	Adverb
o'er	No	No	No	Yes
over	Yes	Yes	No	Yes

As adverbs, o'er and over are synonyms defined as:

o'er (noun)	over (noun)
	(cricket) the division of play during which six balls are bowled at the batsman by one player from the other team from the same end of the pitch

o'er (adjective)	over (adjective)
	having come or been brought to a conclusion

o'er (adverb)	over (adverb)
throughout a period of time	throughout a period of time
	at or to a point across intervening space etc.
	throughout an area
	beyond the top or upper surface or edge; forward from an upright position
	over the entire area