They can eat clover as it is usually mixed in with the grass. The third photo looks a little like dandelion to me which again they can eat. My piggies love dandelion (only the leaves and not the flower) but it shouldn't be fed in large quantities due to the high levels of calcium. Just double check that the third photo of dandelion BEFORE feeding to your piggies.
I am not sure what the first and fourth photo's are so I wouldn't like to comment but I wouldn't feed anything to your piggies that you don't know what it is.
Dock leaves should NEVER be fed to piggies as they are poison.