My advice is offline,because in offline the time taken to complete the syllabus is less,because the teacher knows the children properly because of interaction and by looking at the faces the teacher can understand whether the student is following or not.

one more major point,I don't know how many of you agree,a teacher delivers more quality content in the live classroom,the response of the students will make the teacher to deliver more.

The purpose of writing tests is to compare yourself with the best students of the country,hence just writing the tests alone will not help,enroll in some reputed institute test series and see what rank you get in comparision with others and also take into consideration of the previous results of the institute and see how many get selected. This comparison gets you with an idea as to where your current position is and where you have to reach.

More than sufficient,provided you study for 4 and 1/2 hrs per day in addition to the school hrs.Seriously first finish board syllabus,which will take around three months and seriously work for JEE syllabus.