Yes ,they have fixed shape and volume .it fits the property of a solid that they have fixed shape and volume.
if they hammered or pulled they are capable of breaking because their mass is less.
no ,solids are not capable of diffusing each other.but they are capable of diffuse with liquid.(eg.tablets dissolve in water)
no,it is not possible to compress them because solids don't have space between particles. but in some exceptions, porous solids are capable of compressing. (eg.sponge is compressible due to the presence of pores in them).