Is it common practice to cut through an old hiatal hernia mesh from previous op to perform laproscopic gallbladder removal resulting a hernia-redo?

No. Performing a laparoscopic gallbladder removal would not affect anything near an old hiatal hernia repair. If there was a recurrence from the hiatal hernia, it almost certainly wasn't due to the gallbladder operation.
Hernia. It depends on where the mesh was placed it is best to review the findings with your surgeons who performed the 2 procedures however it is unusual to dissect near the hiatus for a lap chole, it could be he case for an abdominal wall hernia.