Just to answer your first question - I'll leave the rest for the others. Suggestopaedia is a method initially developed by a Bulgarian doctor, Georgi Lozanov, in the 1960s. After working on the use of suggestion in medicine, he applied the ideas to learning. It's based on the idea that we are conditioned to believe that learning is "hard" and that we may fail -and that if we believe that, then our minds will make it a reality. (Parallel that with the story - possibly apocryphal, but it makes the point - of a man who got locked overnight in a deep freeze truck and died of hypothermia. Only at the time the refrigeration was not turned on. But he believed that he was going to freeze to death and his mind created the physical reality.)
So suggestopaedia uses relaxation, positive suggestion and other techniques (eg the tone of the T's voice and games) to overcome those barriers and to replace the negative beliefs with beliefs that learning will be enjoyable and successful. It also uses baroque music, which is said to stimulate a certain type of electrical activity in the brain which is conducive to learning, particularly subconscious intake.
There have been various offshoots of Suggestopaedia, with names like
Accelerated Learning and
Superlearning. If you're really interested then I recommend
this thesis which discusses all the methods and the theories behind them. It's long, but you can always read the conclusion first and then pick out the bits that most interest you - have a look at Chapters 2 and 3 for instance.
I'm not a trained suggestopaedia teacher and I'd never claim to teach via the method. But I do use a lot of the techniques, particularly relaxation, positive suggestion, and listening to dialogues with a background of baroque music, as part of my "ordinary" repertoire of teaching techniques, and find them extremely useful. I'm not making any claims for them as "magic methods" - I don't think such things exist - but they do improve the classroom dynamic and the individual students' attitudes towards language learning. And that can only be positive.