Is there a single word for "one who speaks/boasts a lot about everything"?
I think you may want pretentious.
Not a single word, but my favourite expression for this sort of person is all hat and no cattle.
Some choices:
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know-it-all
A person who behaves as if they know everything
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braggart
A person who boasts about their achievements or possessions
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blow-hard
A boastful or pompous person
(Definitions from Oxford Dictionaries Online)
Poseur comes to mind, particularly if that person doesn't live up to the qualities he or she boasts about.