21.Throw it straight up.
22.The shortest complete sentence in English would depend on whether or not one is merely counting letters and/or spaces. Technically, "Go!" (with an understood "you" as the subject) is a shorter complete sentence than "I am."
23.Are Hobbit riddles free game now?
24.A windmill, or possibly a cathedral.
25.A feather bed is made up of soft down, while a penniless man is hard up.
o_o Got 4 out of the 4 you answered o_o'