6. yes, each level (from 1 to level 5) of the Pickpocket Skill 'mentioned' the LEVEL of the NPC you can pickpocket safety, but if you try to pickpocket a NPC of a higher level he/she will notice you and become angry with possible consequences ... .
With the skill "Know Creatures" you can "see" the level of NPC's and enemies. Read the description of that skill if you wish to know more about it.
There are also equipment items to find/buy which have a boost of 1 point to this skill (handy if you only wish to TRY the skill, but not invest points in them)
Further on I never really used Pickpocket, so I do not know if the "inventory" of NPC's after a while are back filled with items, but I believe if you picjpocked an NPC you can take all his/her items.
Try it if you like it .
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