Quantum mechanics description of Diffraction experiment

The Diffraction experiment carried out in classical physics has been studied again in a more comprehensive manner. The results found are certainly mysterious. First about the experiment: A source of electromagnetic radiation, say light or electron beam is used. For the experiment that I came across in a book on quantum mechanics, an electron gun was used to emit a beam of electrons. An obstruction in form of a crystal with two slits was placed in the path of the beam. And the patterns made by the electron beam after passing through these slits were captured on a electron detector screen. Before discussing the main experiment further let us consider the same experiment done with waves and particles separately, so that we can compare our results for electron beam with either of the two experiments. Diffraction experiment in water waves: A vibrating rod immersed in water vibrates at a constant frequency and produces waves in water that travel towards an obstruction having two openings (similar to slits in the screen of electron beam experiment).After traveling through these openings in the obstruction ,the water waves make a pattern at the detection point. To avoid technical details and keep things simple, let us name this pattern as W pattern. The only thing that one needs to know about W pattern is that since the water waves travel through both the openings, so they show interference. Diffraction experiment in Particles: Since a bullet is of enough large size to be characterized by our brain as a solid particle, therefore bullets were used for studying the pattern produced by diffraction of particles. A gun that could fire bullets at a very fast rate, was used to fire bullets on a wall with two openings for bullets to pass through. Behind the wall was a bullet collector wall made of sand. The bullets after moving through the holes stroked the sand wall and the whole distribution pattern of bullets on the sand wall was named P pattern. It was different from W pattern, in the sense that interference was absent in it as one bullet can at maximum pass through only one opening to reach the screen. At that time there is nothing passing through the other opening, so no question of interference in case of particles.

Thus remember that
Waves after diffraction make W pattern having interference.
Particles after diffraction produce P pattern having no interference.Now come back to the electron beam experiment.

In this experiment the electron beam was released and electrons after diffraction at the slits formed a pattern on the screen. If the observer sees the screen after electron diffraction experiment he sees a W pattern implying that electron traveled as waves from the source to the screen. Now if the rate at which electrons are emitted is decreased so much that electrons come out of the gun as separate particles, and then the pattern formed should be the P pattern. But still the electron particles after releasing from the gun travel to screen and make a W pattern. The pattern has interference in it but how is this possible? We know that a single electron as a particle can only pass through a single slit then how come they interfere to produce a wave pattern. This could only have happened if electron change back into wave form during the course of travel from gun to screen. But they will change to waves only if they sense that they are being released as particles and the observer is observing them as particles at the gun's mouth. So it comes to mind that somehow they sense their state (particle or wave) and no matter what they change their state to waves to form the wave pattern on the screen.
Moving a step further the observer places a polarizer in front of one slit so that all the electrons that have come through that slit are polarized and all the electrons coming from the other slit are unpolarized. In this way the electrons passing through each slit will be identified. Again the electron after leaving the guns mouth came to know about the polarizer and did not change to waves form. The pattern formed on the screen is a P pattern. So, this time the electrons did not change to wave form on the way and continued as particles throughout from the gun to screen. Thus electrons could guess that what measures the observer is taking to study them and maintained their forms accordingly.
Now one more enhancement was made, that that a depolarizer was placed between the slit with the polarizer and the screen so that all the particles that have been polarized earlier are depolarized. In this manner again the electrons passing through both slits would become same and can not be identified as separate particles. But, this time the pattern found was again a W pattern that is having interference. So what do u say?
Electrons come to know that there is a depolarizer behind the slits to depolarize the polarized particles and there would be no way to tell them apart after depolarization, so they again convert to a wave form to produce a wave like pattern.

Whatever change the observer makes in the setup the electrons sensed the change even before reaching that point in space and change their form accordingly. Isn’t it weird?

Now the observer decided that they should separate the experiment over space and time. Now what was done was that there are large numbers of experimenters through out the world with the same setup of diffraction experiment. Now each observer would only release one electron and detect its point of contact with the screen. All observers would do the same thing with a single electron and each observer would obtain a spot marking the striking point of the electron on his respective screen. Now these entire different screens are superimposed. And what you see is the same particle pattern. Now how did each electron know that where to strike and with what intensity, so as to produce a particle pattern after combining spots of all electrons?. All this even when each single electron experiment was done in separate lab and at different time. Don’t u think that it is limit of weirdness?

It has been said that if u understand this behavior of electron in the 2 slit experiment u will know whole quantum mechanics but later the same author has added that since no body till date has understood this weird behavior, therefore no one knows quantum mechanics.