A trace fossil can be anything from a coprolite (faeces) to a footprint. It is anything which proves the creature's existence without being the actual creature itself. For example, an ammonite shell...
Yes. Metamorphic can be weathered away, end up in the ocean and become sedimentary. Sedimentary can end up in a volcano and become metamorphic. It can melt in a volcano and harden, thus becoming...