Hi Mary, the Booth sofa seat cushions have zips, yes, but the sofa covers are fixed. The dark teal option is a 7-day delivery option and is not made to order. The fabric is man made with a textured cotton appearance and can be cleaned with a fairly dry sponge and a weak solution of soapy water. Any stains would need to be professionally removed though.
You can order a free sample of the fabric from the product page at johnlewis.com. Just tick the box as seen below: