I want that my companion thief stealth stuff or unlock doors. How can I do?

unlocking doors might require MWSE, but forcing sneak is quite easy if you have tribunal installed, it adds a "forcesneak" function.

Unlocking doors requires MWSE to get the reference to a non-specific door, in that it's a door that you don't know the tag to, like a tomb door that you didn't add or change the id. As for sneaking, it's http://www.uesp.net/wiki/Tes3Mod:ForceSneak.

I think the meaning was steal stuff, anyway MWSE is probably your only option

this is an interesting problem. I am no scripting expert; but I believe there has to be "built-in" checks for NPC being caught stealing otherwise they can just pick up anything with no problems (like getting a bounty/attacked by guards/disposition lowered)

NPCs CAN get hit with trap-spells, and as such they would then be used for cannon fodder.

ST

to be honest, i dont think you can get an NPC to pick something up without "cheating" in the script.... disabling the item and adding a duplicate to the NPC inventory.

Use AIActivate

wow, never knew it do that, thanks!