Yes you can.
There is supposedly 25 species of pirahna. Red pirahna, red bellied pirahna, red eyed pirahna, black shoulder/ ear pirahna, cariba pirahna(wich is the same as the black shoulder/ ear), piraya pirahna, black pirahna or rhom, gold pirahna or spilo, elongated or pike pirahna, brandtii pirahna, manuel's pirahna, geryi or violet line pirahna and compressus pirahna.
Fry are like children, adults are grown ups.
It depends on the type of pirahna
You got a pirahna with anorexia.
Fry are baby fish that have either just hatched or that have been livebared such as from a guppy. These fry are very small and a called fry because they are not adults
The fish will eat whatever eggs they can find and then they will eat whatever fry they can catch. It's entirely up to you. If you want to save some fry then by all means remove the adults or some eggs or fry to another aquarium. Just remember that the fry will get larger and you will need many tanks to raise one spawning of goldfish.
You have to be 18 to watch the (2010) film pirahna.
only if they eat them or the fry are adults