Registering before the cut off date is one and not the only requirement to enable a student to appear at a particular examination.
In addition to registering within time, a student also has to complete the compulsory coaching requirements (either ORAL or POSTAL) as well as other compulsory practical trainings he/she has to undergo before being made eligible for appearing at the examination.
A student has to complete the procedure involved in the coaching scheme to be eligible to appear at the exam. Thus, mere registering in time would not suffice.