No. Qu is not a valid Scrabble word.
Yes. Speculate is a valid Scrabble word.
Yes, "ax" is a valid Scrabble word.
Yes, "keyword" is a valid Scrabble word.
Yes, "scramble" is a valid Scrabble word.
Yes, "Scrabble" is considered a valid word in the game of Scrabble.
Yes. Ex is a valid Scrabble word.
No. Oz is not a valid Scrabble word.
Yes, "lez" is a valid word in the game of Scrabble.
No. Xe is not a valid Scrabble word.
Yes, "bingo" is considered a valid word in the game of Scrabble.
no