[SixOfSpades]

Most of your questions have already been answered, Aloplex, but to clear up any possible miscommunitcations....

Originally posted by Alopex: How many hour is needed for recasting spell?

The party must have 8 hours of uninterrupted sleep, or their spells will not be re-memorized, and they will still be Fatigued. If you try to sleep outdoors, and you keep getting interrupted by attacking monsters, your party will never get any actual sleep. You'll probably be better off finding a safer place to nap. Later on, in BG2, you will encounter items that can be used X number of times "per day." These items will not recharge themselves after 24 hours--they recharge whenever the party gets 8 hours of uninterrupted sleep.

Is there any tome inside the Ulcaster maze, I got inside but couldn't not find any of them. I saw another haft of the maze but could not find a way to get there?

Yes, the book you want is indeed down there. This is a common problem: There is a passageway that leads to the other half of the maze, but it's very difficult to see because the Fog of War gets in the way. Send one of your party members to go stand in every corner of every room, and that way you can be sure that you're seeing everything.

I got a big trouble dealing with those Fresh Golem because of their immunnity to weapon and magic too.

Golems (of all types) can be a pain, especially for a Wizard. All Golems except the Ice Golem have very high Magic Resistance, so casting spells at them is useless (unless you'd like to cast Lower Magic Resistance, a spell that doesn't even exist in BG1, so I don't know why I'm mentioning it), and most of them are immune to Normal Weapons: You have to hit them with enchanted weapons, or your hit won't have any effect at all. A quick rundown on Golems:
Lesser Clay Golem: Can be hit with any weapon, but is still a decent opponent in a melee. Roughly 85% Magic Resistnace.
Flesh Golem: Immune to all Normal weapons. 90% MR.
Clay Golem: Can only be harmed by Blunt weapons of +1 enchantment or better. 90% MR. Casts Golem Haste.
Stone Golem: Can be struck only by weapons of +2 enchantment or higher. 90% MR, casts Golem Slow.
Sand Golem: Very similar to the Stone Golem, except it might cast Golem Haste (these are rare, so I'm not sure).
Juggernaut Golem: see Sand Golem.
Ice Golem: Immune to all weapons of less than +3 enchantment. Has no Magic Resistance at all, but is immune to Cold, Lightning, Acid and Poison.
Iron Golem: Can be hit only by +3 weapons or better. 100% Magic Resistance, 10% resistance to Physical damage, casts Gas Cloud.
Adamantite Golem: Also invulnerable to all weapons of less than +3 enchantment, has 100% MR, and casts Gas Cloud, but has 90% resistance to all forms of Physical Damage. These things take a long time to kill.

Is there any penalties for wearing the chainmail or platemail(with theaving skill). I got stealth of 100 but can not hide with a chanmail?

Any armor that pureclassed Thieves cannot wear (Chainmail, Splint Mail, Plate, Full Plate) will block all Thieving skills (Stealth, Pick Locks, Pick Pockets, Disarm Traps) while worn. You can still Detect Traps (and Detect Illusions) while wearing heavy armor, but you will have to remove the armor if you want to actually Disarm the Trap. In BG2, Thieves can also wear Elven Chain Mail, which allows Thieving skills to be used, although it does impose penalties (roughly 20%) on thos skills while the Elven Chain is being worn.

Is backstab a skill which I must press to use or it is automatically applied when hiding?

To Backstab:
1) You must be either in Stealth or Invisible
2) You must be using a melee weapon that any pureclassed Thief could use
3) The enemy must be Backstabbable (some enemies, such as Mustard Jellies, cannot be Backstabbed)
4) You must be behind your target.

As soon as you start to attack, you come out of Stealth. Depending on how many skill points you have in Stealth, however, you can still remain 'hidden' for up to a full round. If your attack connects while you are still hidden, you have successfully Backstabbed, and the damage done to your target is multiplied. Rangers, although they can Stealth, cannot Backstab, but all classes get a -4 THAC0 bonus for attacking from Stealth or Invisibility. Note that, due to game limitations, *your* party members can get Backstabbed from the front: The game engine will allow enemies to Backstab you even if they're positioned directly in front of you.

Answers to similar questions, and a whole lot more, can be found by clicking the link in my sig.