If you look at the picture on the boxes id say the main sheet slots into runners each side of the tank, with some sort of hooking device at the top - better check with the seller though, don't take my word for it.
Yes they do Euryale see link as it explains how to install I got mine many years ago and it has a lip thing on the bottom that went into the gravel for support, think it did have some clips but I couldnt use them as my 4ft had glass lips around the top so just cut a grove into the actull plastic plate and it fitted easy enough