There's isn't a "Frozen ATPL" qualification, it's just an industry-accepted shorthand for "Has CPL, Multi-IR, and done all 14 ATPL exams".
You need to have taken all the ATPL exams, but do get some dispensation if you have a CPL (200 hours study reduction, and you don't have to retake the VFR comms paper). It's all in LASORS
, Section G. This is the ATPL section, but it's relevant as that's what the "Frozen ATPL" stage aims towards. Effectively, you have the qualifications to get an ATPL, but you don't have the hours (500 multicrew, 1500 total plus the ATPL skills test).