Do all cells perform various jobs

Yes, all cells do in fact perform a specific job, if a "cell" does nothing, it is most likely not a cell.

There are different types of cells and they all have their own role. For example, white cells fight with all the germs and viruses. Did you know that if you get chicken pox once, it is more likely you won't get it again because the white cells would know how to defeat them if that incident occur again.