yes.
Anything in a cell that provides a function for the cell is an organelle. If it is just there temporarily, like food, than it is not an organelle.
it is the nucleus.
Mitochondria, is the Powerhouse of the cell
I am not exactly sure, but i think organelles made when a cell is made, or reproduced. Organelles are a nesscesity of cells and just come when a cell is made.