"The man was hung at dawn." "The man was hanged at dawn."
Are "hung" and "hanged" entirely interchangeable?
"The man was hung at dawn." "The man was hanged at dawn."
Are "hung" and "hanged" entirely interchangeable?
No, they are not entirely interchangeable.
Hanged is the correct past participle of hang = execute.
Hung is the correct past participle of hang = suspend. It is increasingly used for hang = execute as well (possibly as an over-correction as hanged is odd), but where there are two words with distinct usages, it's a great pity to confuse them.