Multi crew means more than one driver, so your ERJ counts. It clarifies the difference between transport jet time and single pilot jet time, usually referring to the military types.

You mention 'second crew', so perhaps that clarifies as normally second crew, to me, refers to ultra long haul's legal requirement.

Frozen ATPL is something they have in the UK and the like. One can write ones exams well before having the requisite time requirements and thus, your ATPL licence is 'frozen'. Cooky isn't it.