Hi, these are some of my doubts
What happens when a character uses a non profiency weapon?
This is on Page 205, top right under Untrained attacks:
When a character makes an attack without the appropriate
proficiency, the attack is “untrained.” Any character may make an
untrained attack, but he suffers a –4 attack check penalty and his
error range increases by 2.
Any character can use anytimpe of armor only restricted by whis origin and the penalties the armor gives, right? There are no Armor Proficiencies?
Is the Spellcasting skill "universal"? A mage can cast ani spell its level and class allow regardless of Schools/Disciplines?
For the Mage class, yes, there is an upcoming book (Spellbound) that will add classes that are restricted by school/discipline, however.
Does having a School or Discipline Knowledge gives any spellcasting bonus while casting related spells?
(A mage having knowledge of the Channeler School and the Force Discipline, casting Fly I has any benefits?
No, though there might be some confusion somewhere, because I don't know what you mean by knowledge of the Channeler school- there are benefits given to classes that can only cast a few disciplines (check out Way of the Crucible in Alchemist on page 53) but none for Mage.
What are the casting techniques?
I don't know what you mean here, if you're referring to the Knowledge:
section under the Spellcasting skill, those are things your character, when making a Knowledge check about them, may gain a bonus from his Spellcasting skill to the Knowledge check.