Identifying shellfish/ coral fossils

[cpper]

Hello

I found the specimens attached below in central Romania, in a nature reserve known for the presence of fossils. Could I get an ID for them?

 

Specimen 1, is this some kind of coral?

Specimen 2 has the shape of a tiny turtle

Specimen 3 looks like a most common shell 

Specimen 4 was found in another place, on a river bank. Could it be petrified wood, or is it just a rock with an interesting patter?