Question

What is hollow gut . Is there any difference between hollow gut and gastrovascular cavity?

Answer 1

Hollow gut is gastrovascular cavity opening.
Ther is no difference between gastrovascular cavity and hollow gut.

The gastrovascular cavity is the primary organ of digestion and circulation in two major animal phyla: the Cnidaria (including jellyfish and corals) and Platyhelminthes(flatworms). The cavity may be extensively branched into a system of canals. In cnidarians, the gastrovascular system is also known as the coelenteron, and is commonly known as a "blind gut" or "blind sac", since food enters and waste exits through the same orifice.