Questions on stealth, how does it work (combat and movement)

I don't know much about how stealth works, like how would someone go behind someone and choke them unconscious and does a stealth attacking work on an NPC, can you instant kill someone or knock them out instantly?

Try asking general 2nd Edition questions over here on Dragonsfoot 2nd Edition forum because they have a larger community of experts on the game rules, game system in general. DF forum is set up to accommodate the myriad rules questions that come up, and in fact they probably already have a long thread discussing stealth and backstab and choking moves. The Tavern forum I'd like to keep focused to How To Use Roll20 in your 2E online play, if that makes sense. DRAGONSFOOT 2E FORUM LINK <a href="http://www.dragonsfoot.org/forums/viewforum.php?f=" rel="nofollow">http://www.dragonsfoot.org/forums/viewforum.php?f=</a>... Regarding how to implement it in Roll20 gameplay in a 2E game, that's another question perhaps, and this would be the best place for asking that. If you want to talk more about that, please feel free to elaborate.

well in my mind say you got a thief, if he can move silently out of line of sight of target. if he moves silently from behind he's got surprise. Backstab, even at level 1, double damage so even with a dagger, 2-8 HP. if your civilian has 1 or 2 hit points, that's it. Esp if you say iron man rules 0 HP = death, not that -10 to bleed out. Low level rogues can wade through guards, if they are careful and lucky. if you have higher level corporals and sergeants, it's a lot tougher or you need a higher level thief.