Yes. The prefix mid- is hyphenated when it is used with numerals or written-out numbers. For example, the mid-twentieth century.
yes
No, in general it is not correct to hyphenate certain prefixes, co-, pre-, mid-, de-, non-, anti-, etc. You therefore write preordain instead of pre-ordain, antidote instead of anti-dote, and midnight instead of mid-night.
It should be hyphenated when it's being used as an adjective. For example: nineteenth-century writers.
Yes, "mid-July" is hyphenated. The hyphen is used to link "mid" and "July" to indicate that it refers to the middle part of the month. This helps clarify the meaning and ensures proper grammatical structure.
In this use of the medical terminology, "mid-left" would be correct. This is likely only an issue in a thesis or published article, as the reference is clear either way.
From the mid-6th Century to the mid-4th Century BCE.
No, "mid-nineteenth century" is not capitalized unless it is at the beginning of a sentence.
Don't hyphenate; ongoing is one word.
You hyphenate it only at the hyphen.
I think it's more accepted to hyphenate it.
You do not need to hyphenate.