Hi syzygy, pretty sure you'll parse 18 if youlook at it fresh. Re the playfair cypher, without wishing to appear condescending it is relatively easy here if, as you have done, completed all others and know the 4 words to be coded as the preamble tells you it is 1 word and the information gleaned leads to it with few inferences/educated guesses having to be made. Should you decide to proceed and not succeed, I think highly unlikely, email me (save spoiling for others) and I'll take you through the steps I used.