Does the MND stat effect all types of magic defense?
What other kinds of magic defense are there? I only know of "magic defense." MND doesn't affect "Magic Damage Taken -" nor does it affect magic resistances.

Does stealing from behind an enemy increase the chance of stealing from them?
No. Whatever gave you that idea?

Question: Does putting 'For the devs" in your topic title increase the chance they'll answer the questions?
Answer: No.