Yes, NCERT best book for all classes.
Yes NCERT books are very good as they use easy language to make the students understand the concepts
NCERT books are important since they will help you as per the CBSE syllabus. In class 6th onwards exams and assignment are suppose to use all questions only from NCERT and no where else
yes they are important
The books are good from the point of view of doing activities and practicals which help to further clear the concept