To feed a cherrystone clam to a green spotted puffer fish, you just give it the whole clam. Puffer fish are able to crack open the clam and eat what is inside.

can cherrystone clams be eaten on the half-shell

Purple-shelled clams, called cherrystone clams or mercenaries, are a species of clam commonly found along the east coast. Small cherrystone clams start out as white when small, but turn purple as they grow larger.

No.

Little neck clams are smaller than Cherrystone clams.

There is a picture of them, If you observe closely, The littleneck seems a tint bit smaller.

Cherrystone Bar Light was created in 1858.