Registrar

1). If we already have a TIN no. & we are not carrying out any business activity since long then is it necessary to get up through migration?
2). Moreover, if we right now surrender the TIN no and there will be no such requirement of migration, so can we do so? Then according the limit of 20 lacs under GST we will not be required to get registered under new regime from 1st of July. So is it advisable to do aforesaid?