As stated in other answers, some of the ideas from your question are impossible due to the different points of view, beliefs and thoghts of everyone, for example:
- A world where all the observer wants is true: if I want to be rich and someone feels envy from my wealth, desiring my poverty, the physics of this world would be in conflict.
But... this leds to a new idea for me, where you could complete the "laws" of this universe stablishing some priorities, like some "karma gravity" making the "good" people (in a global moral/ethic way) to get their desires come true prior to the desires of an "evil" man with opposite ideas. "Karma" could be changed by age, weight, etc.
Similar things happen in the following ideas:
Every universe where everyone can define/created/generate changes, matter, feelings by their minds will (unconsciously or not, represented by fears, desires, ideas, etc.) will suffer by the opposition and the non-coincidence of the different people thinking.
Finally, we left with "the world where all the observer believes is false".
In my mind, this option you propose can be perfectly plausible, as René Descartes stated:
"I suppose therefore that all things I see are illusions; I believe that nothing has ever existed of everything my lying memory tells me. I think I have no senses. I believe that body, shape, extension, motion, location are functions. What is there then that can be taken as true? Perhaps only this one thing, that nothing at all is certain.", Meditations on First Philosophy.
In our universe already, we can suppose thet our beliefs are false.
In order to comment an example, we never live the "present itself". We are always reacting to what happened a few microseconds (if we are looking at something a few metter far from us), a few minutes (properly, eight minutes if we look for changes on the Sun surface) or hundred of years (300 years, approximately, if we look at Polaris star in the night sky) back in time. We will never know what happening in "real precised" real time.
We can also asume that our senses are not perfect. Is our blood really red? If nobody tells the colour blind people about our different (and more frequent) perception, they would defend that blood is blue. Are we all colour blind compared to another race? Who is the truth owner?
It should not be difficult for the writer/story designer to make that the reality everyone perceives is wrong (partially at least). Every mistakes/misbeliefs could get assembled all as an entire lie for all. What makes me remember a couple of examples...
I hope you can find inspiration to create your world with this.
Good luck! And don't let your sense lies to you... too much.