Actually doubt clearance setup is best only for medical students, in jee section there are less teachers available for doubts.
Coming to other questions,
A1) Top batches get additional questions, Quizzes, class test apart from sheets and races.
A2) practice sheet is seperate chapter-wise sheet which include exercise S1, S2, O1, O2, JM, JA and some basic theory along with solved examples
A3)Given one are sufficient for almost every chapter, if you are in a good batch you will get additional stuff as mentioned in A1, there is less time left after completing homework. Few chapter where sheet is not sufficient teachers advise books by themselves.
A4) Teachers are supportive, I can assure that and they motivate from time to time.
A4) Test are conducted once in every 21/28 days till syllabus completion. Then during SCORE program(It is a revision program by ALLEN) tests are conducted once/twice a week.
Do ask anything else if you need to know.