In a coral reef. Ex: the Great Barrier Reef off the coast of Australia
No, sea sponges are not decomposers. Sponges are filter feeders.
no sponges are not unicellular.
no sponges do not have bones
No, sponges are not parasitic.
Sponges are asymmetrical, although a few species have nearly radial symmetry.
There are thousands of different types of sponges, so there's not enough room to list them all. Here's a great website showing several hundred different sponges found in the Caribbean so you can get some idea of the different groups they fall into.
To answer your question no sponges do not hibernate
No. Sponges are animals, which are heterotrophic.
Yes sponges have organs.
No sponges lack organized multicellular organs, such as nerves and muscles.
If you're talking about kitchen sponges, they do not have cells. However, sea sponges have cells.