18 Canons, criteria, rules. C, cold, Rite, form of worship and Ria/air backwards (retrogressive look).
24 G, note (musical) and Ibo, W African tribe(uprising = upwards). Gobi, desert
27 Shoo, drive off, A, adult, MP, member. I haven't checked in my dictionaries to see if Shampoo can be a massage!