the 02A gearbox was first introduced in roughly 1991/92 used in MK3 Golf / Passat and MK2 SEAT Ibiza as well as a few others up untill around the 1995 year, then they introduced the 02J gearbox up until roughly 2003
Both the 02A & 02J are 5 speed,
some very early 02A were clutch cable but was soon changed to hydraulic clutch same as 02J
Normally have cable select operation between gear stick & gearbox rather than rod.
Both the 02M & 02Q are normally 6 speed, started using the 02M in 1998/99 in MK4 Golf & MK1 SEAT Leon then roughly in 2002/03 was upgraded to the later 02Q gearbox. Both are cable select operation.
Think the early 02M gearbox alloy housing/casing is known to crack on the high performance models, think there's a company called Darkside Development's that make a reinforcing plate/bracket, to help against this failure.