I love a bit of pedantry but there's no case in which it's singular. The term refers to peoples belonging to one of a group of aboriginal nations and using the singular without instead referencing an individual nation is a bit nonsensical.
The clue could be worded correctly or incorrectly, as it refers to "a group" which could be either one specific First Nation within the larger First Nations or a grouping of multiple First Nations. At the end of the day "a group" is non-specific as to its meaning.
A ship's second-in-command can also be a First Lieutenant if it is a warship. Either allow both terms or make it clear it is a merchant ship being referred to in the question
The first amendment does not grant the right to free speech, nor does any amendment grant any rights. Free speech is a natural right and the Constitution merely guarantees it.
Could we accept (first) Folio for the book question? Wikipedia calls it one of the most important books ever published, and I believe I've seen videos and articles about rare, highly sought after early editions of the book.
First contact threw me, although I guessed it. I've only heard it used to refer to the first contact between Indigenous peoples and outsiders. Is it really better known as a term for something that has never happened and never will happen?
Jewish double portion heritage: First Born