Grimrock

There are 3 secrets doors to open on the "prepare to fight" room
And then, put 3 objects on the 3 plates

I've drop myself down to lvl 8, solved all riddles regarding green gem there and got back upwards. But I have a problem with a room on lvl 4, where are 9 pressure plates (which are pressed only by items, not while walking). There are 3 torches/torch holders attached to the wall, which seem to be turn on/off after pressing plates. Three questions about that:
1. Is it a secret or obligatory part to progress through?
2. All torches are shining so I assume that I should put them out?
3. What is the correct combination of plates to solve the riddle (if it is a riddle and not a red herring)?

1. Mod focused on combat (sometimes very heavy)- I still wonder how somebody on this forum was able to finish this on hard with default party in 12:30 hours time. Man, you rule!
2. Ironically this mod is less "chaotic" than The Master Key IMHO , where sometimes I had serious problems with finding proper keys and ways to go. Of course I was lost there too (mainly on levels 3-5) but always was able to find solution.
3. Most hardcore/favourite FIGHT parts:
- Lvl 10 with hordes FIre and Ice Uggardians- Dragon fight and 3 Ogres in one room
- Lvl 9 with Dragon Fight- reaally scary, running near walls and avoiding all those big motherf.ckers was hard, but satisfaction after killing all of them was immense
- Lvl 8 (including The Deep Trip part). Most of Grimrock players hate spiders, but I love to fight against them- The Deep Trip is one of the most epic fights in this mod
- and the winner is- OF COURSE THE MOST EPIC COMBAT IN WHOLE MOD- LVL 1 battle against swarm of monsters. Man, that was really hard and loong (but when i found room with teleporter in NE corner epic battle turned into easy fight- i lured monters into room, closed doors and killed them one by one)
4. I didn't liked:
- feeling of emptiness in lvl 9
- lvl 3 part with shooting skeleton archers and moving walls- annoying
- lvl 7 and lvl 11 respawning skeletons with no XP for killing them- that sucked a lot
- ice dragon in lvl 13- I wasted almost an hour for killing this bastard
- final fight was irritating with those respawning mummies- you could really create something more intriguing.

What i really liked:
- solution was always near and when I get lost it was always my fault (I was to lazy to see the map). This is what annoyed me in The Master Key, where I often couldn't figure out proper solution.
- Ambient music was great (I am fan of metal, but I also love to listen good ambient) and fit into the climate of mod perfectly
- I don't like too complicated puzzles- puzzles here are sometimes hard, but not impossible to solve
- some cool stuff to buy in shops- great idea

Stuck at level 4 where there are double doors, i managed to trap 3 enemies to get 1 key, but i am hopelessly lost when it comes to the 2nd door.