Dr Tall swoops to the rescue! (It's been a while since I've gotten to say that :D)
1. I belive current speed is stored in level info (7). I am not totally sure. It's either (6) or (7). Since you're new, I don't think it would hurt to remind you that the first info box is info (0). All info box counting starts from 0 not 1.
2. Make a passage you can't go into?? I'll assume that you mean can go into. You need two passageways of the same type. You can NOT use one normal and one ornate unless you'd like to reboot your machine. See where it says "Sprite X of #" ? The "#" is the total number of sprites in your level. The "X" is that sprite's Sprite ID. Simply cross the sprite ID's into the info (0)s of the passageways. If that's confusing:
Passage #1
Sprite 35 of 124
info (0) = 46
Passage #2
Sprite 46 of 124
info (0) = 35
If you really did mean can't, then make the passage refer to itself. (So just put its Sprite ID as its info (0).)
3. Sigh.....do you really want to do that? OK here goes. The "speakable characters" in Ferazel's Wand have their own range in the sprites file (2951-2999). Any speakable character MUST have their sprites in that range. So you want a tree? First, get your tree design and copy it to the clippboard. You must have its sprite, and its mask (the sprite just w/o color and all the space you want it to cover being black.) ready. Open the Ferazel's Wand Sprites file and the MASCOT editor graphics file using Res Edit. Paste your tree sprite into any number from 2951-2999 in the Sprites file and in the MASCOT editor. There is no restriction to this except that the numbers MUST be the same. Then paste your mask into only the MASCOT editor graphics. Your tree's ID must be whatever its sprite ID was but x10. So if you put it under 2966, its mask is under 29660. If you want to be sane later, be sure to name the sprite file in the MASCOT editor grapihcs (go to resource info) Now, if you did all that right, when you re-open MASCOT, your tree should be in the objects menu. Select it and, bang! A conversational tree.
4. Umm....well you could set all the tiles to pain causing and make the damage enough to kill Ferazel no matter what......I think what you'll find more useful is just using death powerups. I think a poisioned item is what you're after and that is not possible.
5. Signs are not associated with plaques. That is everyone's mistake. (I'm not even sure I have them totally straight :redface: ) My understanding is this: A plaque and a roadmap and everything except for a sign are actually speakable characters. Use their info (0) to indicate a conversation ID. The sign runs off of STR# resources in the World Data File. Open it in Res Edit and find the STR# resouce and open the one called "signs". Scroll to the bottom and click on the stars at the very very bottom of the list. Then go to "resource" and select "insert new field". Type whatever you want your sign to say. Then, in the sign's info (0) insert whatever number STR line that was.
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Dr. Tall says: Taller is Better
(url="http://"http://drtalll.tripod.com")Dr Tall Land(/url)
Isn't Dr. Tall awesome? 
Is there any way to decrease a user's max HP after you give them HP?