Yes and no. The out-of-plumb wall should be hyphenated while the wall was out of plumb should not.
It should be hyphenated.
No, the phrase "thank you note" is typically not hyphenated when used in a sentence.
Yes, one-on-one is hyphenated. I don't know why, exactly. It just is.
No, the phrase "top of the line" is not hyphenated.
The second word should not be capitalized
yes
No, "year long" is not hyphenated when used as an adverbial phrase, such as "The project will last year long." However, when used as a compound adjective before a noun, it should be hyphenated, as in "a year-long project."
No, the phrase "hour and a half" is not hyphenated when used in a sentence. It should be written as three separate words. However, when used as an adjective before a noun, it can be hyphenated, like in "an hour-and-a-half meeting."
Yes, end-product is hyphenated. It is a noun and treated as one word which is hyphenated.
No.
The phrase "plumb forgot" likely originated from the use of the word "plumb" as an adverb meaning "completely" or "absolutely." In this context, "plumb" emphasizes the degree to which something is forgotten. The word "plumb" in this sense dates back to the 16th century, while the specific phrase "plumb forgot" likely emerged later as a colloquial expression to convey total forgetfulness.
Yes, "half-page ad" should be hyphenated to show that "half" and "page" are acting together as a compound adjective to describe "ad."