QM tables-Task List Group counter- PLNAL & PLNKN

I am working to get a report for PM Calibration report, I have to link these 5 tables- EQUI, QAPP, QALS, PLMK and QAMR to get Insp. lot result data, my queries are:

a) QALS-PLNAL (Task List Group counter) and PLMK-PLNKN (Task List Node) are same thing?

b) which field should be used for MIC/Char seq. no. matching -MERKNR or ZAEHL (internal counter)?

please suggest and all of above if any other better idea is there, please share.