How are unicellular organisms different from a cell colony, and a colony from multicellular ones?

The main and distinctive feature of unicellular organisms is the unicellular structure of the organism, i.e. a cell, in fact, is a whole organism that has and performs the same functions as a multicellular organism.
Colonies are rows of protozoa (unicellular) – in this way they resemble multicellular, but they are not, since the cells of colonial forms, although they can connect to each other by cytoplasmic bridges, are always located in one layer and remain undifferentiated.