Tidy Cats Breeze Cat Pads 4 / pack

we have a cat that was dumped in yard three years ago. was an outdoor cat. about 10 yrs old. can't get it too use the cat box. likes to go out @3-4 am

Are the pads biodegradeable?

why is the 4 pack cheaper than the 10 pack

Do the pads have a liquid-barrier on the bottom or does the urine go through? For under my cat's box to catch urine when she pees over the edge.