1) When a character has a special ability or effect that let him take an enemy or a stranger as a follower, what are the consequences if he dies and leave them on a space? Does the other characters need to fight again with all the enemies in order to get his lost objects?

2) Do followers that does not have the word "follower" in their card (such as enemies that are not taken as throphies or automated followers of the Tinkerer) can be killed or be captured in the dungeon cell?

3) Can the automated followers of the Tinkerer be taken by spells or special abilities because of the fact they are followers (even if they are actually objects)? For example by the Sorceress special ability.

I suggest you take a look at the current FAQ and check the paragraph "Cards that become Followers":

http://www.fantasyflightgames.com/ffg_content/Talisman/support/faq1-1/Talisman%20FAQ%201-1.pdf

This has interesting consequences for the Tinkerer. Automated Followers cannot be taken by any means, because they are no Objects anymore, but are Followers only for the Tinkerer. Still they keep their Weapon and Armour keywords.