Whole conjugation is actually:
Mutlu muyum? Mutlu musun? Mutlu mu? Mutlu muyuz? Mutlu musunuz? Mutlu mular?(or Mutlular mı?- both are possible)
"Mutlu mular" is TERRIBLY WRONG. It is a mistake you may encounter time to time in daily speech by people who don't read much. If you make that mistake in writing, it will only show to the reader that you don't read at all or you dropped out of primary school!
The mistake is putting the plural suffix(-ler, -lar) after the interrogative particle(-mı, -mi etc.)
"Mutlular mı" is correct.
You mean "Do I look happy?" I guess. That is "Mutlu mu görünüyorum?" or "Mutlu görünüyor muyum?". The difference is the former means you don't really want to look happy, latter means you want to....
If it is only a single person that you can refer by "sen". If it is plural or someone that you need to show respect or some formality, it should be "mutlu musunuz?"
Is the pronunciation of "mutlu" typical/correct? I can barely here an "l" there. The "müyüm" is also quite contracted, but I have grown accustomed to that by now. My first transcription though would have been like "Mutu mim".
In general i am still confused I would like to know when i have to use musu, mu,mi,musunuz........ Thanks
The "m*" question word works like a "..., do i/you/he/she/...?" In English.(Or the analogous phrase when the predicate uses an auxiliary verb like "have/be/...") . It turns the sentence into a question. Just like you have a personal pronoun in the English case, you have a person suffix in the Turkish question word. And the vowel is determined by vowel harmony rules, as if the question word was a proper suffix to the final word of the preceding sentence. Hope that helps...