Matthiola incana/Stock

Googling indicates that all parts of the plant (especially the roots and seeds) are extremely poisonous and wearing gloves to handle it is recommended.

Yes these are Dahlias, the 3 on the left are formal decoratives and the one on the left is classed as a straight cactus. The link below shows the names, classifications and pictures of many different Dahlias. Looks like the photo was taken at a Glad and Dahlia show. Here is a link that might be useful: Dahlia Classifications with photos

I can't tell you what their names are but I can tell you they need to be either put in the ground or into much bigger pots. That last one looks like either Double Delight or Cherry Parfait, maybe.