What is the job or function of cell walls in plant cellls

The cell walls in plant cells provide tensile strength and protection against mechanical and osmotic stress. It also allows cells to develop turgor pressure, which is the pressure of the cell contents against the cell wall.
Source:Nature.com

Decomposition is the cycle at which bacteria breaks down any organic material into the soil

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.