As modular you must have a PPL before commencing an ATPL ground school theory class. You do not have a Frozen ATPL when you complete the ground school, to have a frozen ATPL, you must have a CPL/IR with the ATPL theory completed, this will then become an ATPL once you have completed 1500 hours of flying whilst ticking other boxes also.
There is also no such license as a Frozen ATPL, it is just a nickname for having a CPL/IR and ATPL Theory under your belt, but not having completed the 1500 hours and other requirements.