Higher to lower gradepay without NOC

As per DOPT guideline age relaxation of 5 years is permissible for appearing in exams conducted by SSC to any govt. employee serving continuously for not less than 3 years. At the same time, NOC is not given for joining from higher to lower grade pay. Now for an employee who is already serving in 4800 grade pay who wish to join a post of lower grade pay of 4600 and claim age relaxation for appearing in the exam simultaneously, is it permissible? If the employee proceeds without NOC will his past service be counted for claiming age relaxation? Is there anyway to achieve this? Can CAT be moved if NOC is denied?