There are many small fossils on that rock. It would be hard to tell what the rock itself is from just the photo. Limestone is the most likely candidate.

You could test if it is limestone by putting a small drop of very strong acid on it and seeing if it fizzles. Hardware stores sell muriatic acid (scientifically called hydrochloric acid) usually as a pool chemical. One drop from an eye dropper would be enough to tell definitively that it is limestone.

It would be incredibly difficult to determine the age without conclusively identifying a shell from a specific era. This is known as a bio-marker. A professional paleontologist who specializes in paleostrategraphy might be able to do it – but they trypicallt cost about $200/hr and work for giant oil companies.

If the sample is very young, like less than 100k years old (yeah, the geologic timescale calls that young), then you might be able to carbon date it. But that’s assuming it is limestone or there is still some carbon remaining in the shell material itself.

But, yes, fossils. No, dating it is difficult. Unless it is of academic interest, it’ll cost a fortune to date. There are millions of rocks like this, and it is unlikely to be unique, except to you ;)