seven because that is how many tiles you have.
paganpaintpandapanelpanicpansypantypapalpaperparkapartypastapastepastypatchpatiopatsypausepayeepayerpeacepeachpearlpecanpedalpeevepenalpencepennypeonypeppyperchperilperkypeskypestopetalpetitpettypeweephasephloxphonephonyphotopiano
None, there is no such letters in the English language.
womanize
There are 26 letters in the Scrabble alphabet.There is one alphabet, consisting of 26 letters, in Scrabble.
There are many hundreds of words that contain those three letters (e.g. mudflow), but there are no English words that contain the letters MFW all together.
four
3
Burros is a legal scrabble word. There are no other English words that contain that exact pattern of letters.
mitzvah
79
In a game of Scrabble, each player starts with 7 letters.
There are millions of words that contain the letters "th."