EXTRACT Data, Left Side of Character "/" - various conditions

Hi,
I want to Extract Data from Left side of character "/"
Data looks like :

12345678/001
BKJ12345/009
JG123456/099 - name 2
77661199/008 - name 1


01. IF all are Numbers (...all in left side of "/")
02. IF first two are letters and the rest numbers (...in left side of "/")
03. IF first 3 are letters and the rest numbers
04. IF Left side =K2 (data in K2)

Thank you all