Yes, it is a compound adjective and should be hyphenated. In that context, 'hard' is an adverb modifying 'working'. If you do not hyphenate it, you are using two separate adjectives, 'hard' and 'working'.
If you look at Merriam-Webster it cites 'Hardworking'. As A Brit, I would use 'hard-working' (as cited in the Oxford Dictionary). However, neither is incorrect.
Both can be used.
No, "hardworking" is not hyphenated.
more hardworking, most hardworking
Hardworking as a dog or beaver cuz animals word hard or hardworking as a builder cuz they work hard to build houses and buildings?
Hardworking is the correct spelling.
It is not hyphenated.
John is very hardworking
Motorcycle is not hyphenated
No it's not hyphenated.
words are only hyphenated when they have a separate meaning when separated than they do when hyphenated
They are hardworking because they live and die to work.
Yes it should be hyphenated.
It can be. Some words can be seen both hyphenated and non-hyphenated.