SureAI

Sorry don't have the map as I don' have any save in that part of the game.
But I do remember that all the stones are in the VERY SAME room with the holes. And all the holes are only in this one room infested with rats (may sound obvious, but when I first did this quest I tried to find more holes in other parts of the mine;p ) And the stones were placed close to the holes.
Just try throwing the blocks into the holes. When it fits, you won't be able to move the stone.
There should be 3-4 stones in total, as far as I can recall.
Good luck !

i recall 3 stones myself. as for the stones only fitting where they're suppose to go, i heard that the smaller stones can fit into the bigger hole, leaving you stuck if that happened. didn't happen to me so i can't confirm it.

This can't happen, logically, except the engine bugs. (We have some reports of the engine bugging, however.)

OK I bricked up the rats--by sheer accident. I had to use the tgm/god cheat to stay alive. The bricks go in the top and bottom niches of that final room, plus one at the N W corrner. The z key was hard to use because I kept hitting the ceiling, and the rats pushed the bricks out of my way--I think they pushed the bricks in by accident.

Now, after getting the soap for the guy, I go to the guard for "tasks" but he is angry and only shoos me away. So I can't proceed. What went wrong?

Did you talk to everybody in the mine before talking to the angry guard?

Also, what do you mean by "hitting the ceiling"? Custom race?

After receiving the reward from Karrick (the one with the helmet problem) you should speak to Merre in the mine. He will state that he has no more quests, you should ask Mortem (the guard) now and he should mention a problem with the gate.

I spoke to Porim, then I had the quest from the guard to the other mine section.
There was another magic symbol in there.

Now at the abbey, quest to the Clatter cave: I can't see the goblin I'm supposed to target, and I can't seem to hit the door lock. So I might go to the boar quest instead.

The game seem to swing from King's Quest simplicity to impossible. Does the difficulty slider have much effect? In the rat cave the rats were under my feet, preventing movement. I would try to jump over them but seemed to hit the ceiling?

The difficulty slider has at most 100% effect, i dunno how much exactly. Its been weakened a lot.
You can only change to the boar quest, if you got a savegame before accepting the goblin quest.
About the door: you need to hit exactly the lock, not just the door, so you need to take a little aim.

@Rats: I'll see whether I can fix this. Thanks for explaining the bug.

@Game difficulty: There is a nice training ground for levels 4-5. It's somewhat hidden though.

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Go from the Abbey to the Faldrin fortress, and turn left just before the fortress.