it would be a organism.
Amoeba
No it can not.
Organism.
no
One example of a cell that can live on its own is an "organelle." Organelles are found inside eukaryotic cells and perform specific functions to keep the cell alive and functioning properly.
they can make their own food and adapt to their environment
no
No, I do not have any friends that own a dakota sport. There is no need for one where I live.
If see practically, no. Because a cell is a living thing that means it has some input and output for surviving. Even if a cell has enough reserves stored to live for a period of time it would die after that; a cell needs some resource to live.
paramecium cells can not survive on its own because it works as a group while on the other hand, the Elodea cells can live on their own because they are single cells.
no because it is part of a much larger being
Nothing smaller than a cell that can live on its own has ever been discovered. Viruses, for example, while smaller than a cell, cannot live on its own. It it not even sure that viruses are more than a dot of inert chemical.