Discussion topic 2.
I normally do the same as teacher A: I do not like to interrupt my students when they are talking, although they normally notice they had said something really, really wrong just looking at my face. If I think it is necessary - depending on the type of mistake and on the level of the students - I mention the problem when he/she has finished and then we try to correct it together. I also praise them if they have corrected themselves while talking.
Discussion topic 5.
This is something that I often do after the students have handed me a written task: I only mark the type of mistake on their writings (e.g. tense, grammar, word order, missing word, spelling...) and when I give them back the papers, I write many of their own sentences with mistakes on the blackboard (I choose those mistakes which come up most often and which theoretically should not have been made). The students then try to correct all the sentences together. We do this orally, or somebody comes to the blackboard... it depends. When we have finished, everybody has to correct their writing. If necessary, with the help of a classmate.