2) Build both floodgates and the lever. Link the lever to one of the floodgates then pull the lever. That floodgate will open then you link the same lever to the other still closed floodgate.
There is something about this game that invites answers when the poster has never had any experience with what they're saying, just making something up. I did the same thing when I first landed, with the same confidence, and just as dead-ass wrong.
Newbies - DF is not "logical" in the way of "common sense". Don't guess. It has a logic, but it's all its own, following its own rules. Learn those rules, don't guess, save yourself headaches. (The Wiki is a good place to start.)
3) A raising bridge can be built without a channel and when raised will act as a wall. EDIT: Be sure not to lower it onto anything you want to keep.
Correct. With one exception
1, levers don't "toggle" on/off - they have an "ON" state, and an "OFF" state. For doors, floodgates and hatches, ON = OPEN and OFF = CLOSED - there is no way to get them into the opposite phase
2. However, for bridges, ON = UP and OFF = DOWN, so, as Z correctly suggests, if you connect a door and a drawbridge to the same lever, ON = door open and bridge up (shut tight against a hallway), and OFF = door shut and bridge down (opening the passage).
Make sure the bridge is more than 1 tile long - don't worry about "height" when it's up. (Say it with me - Forget your logic, learn DF logic.)
1) mechanisms attached to levers toggle on/off, regardless of "state" of the lever.
2) if you do, they simply don't respond until the lever is in the correct phase.3) Is there something I can use to block off the 3-wide path to my underground trade area when it isnt in use?
You can build a drawbridge at the front, but if you're playing vanilla DF, just carpet the entrance with traps. Make sure there's an L or two to protect your mechanics and haulers who clean up after the gobbos rush blindly into them. Eventually a siege might come that is truly a wave attack, but BY THEN YOU WILL HAVE MILITARY. (That's a hint.)
5) What should I make with a vein of aluminium that I found to make a profit?
Don't trade it - you shouldn't have to resort to that.
Aluminum is tied as THE most valuable substance (short of adamantine). Save it for your most skilled masons and/or mechanics to make Statues or Mechanisms, and then install those where the Created Wealth will add to your migration waves - more dwarves for the machine.
For trading, put your mason on making rock mugs for a season - that's all you need at first, and later you can trade away useless goblin clothing too.
7) Is it possible to capture wild animals suck as camels that are wandering the map (They are not tame, they were on the map when I arrived)?
Yes. Make a large X-shaped barrier on the map (walls, channels, or removed slopes), with a passage at the intersection, where the "X" crosses. Put your cage-traps there.
All of these questions and more are answered in the Wiki, with more related questions that you haven't thought to ask yet. Read the wiki, it is your friend.
In the above cases, recommended articles are found by the key words in the questions - evaporation, trade, aluminum, animal, trap, etc etc.