2. chopper engineOn true
where chopper is the name of the vehicle you want to turn on.
3. In OfP you can't open doors or ramps. If you're using an addon you must read the addon documentation, but usually you can do that with the
action command (but you must know the addon action name to lower the ramp and/or open hatches and doors)
4. I don't completely understand this question but I think you wanted to say that you want the game to detect all the objectives are completed and then end the mission by the end trigger (the end trigger is the only way to end a mission). For this you must write a small script, that is you can run a script every time you complete an objective, set a boolean variable to true for every objective and set the object as completed so that you can see the green tick in the notepad. For example when you complete the first objective you run a script from a trigger with this code:
objVar1 = true
"1" setObjStatus "DONE"
exit
but you need to know how to make scripts to fully understand this (if you want to make decent missions you need to know OFP scripting language). The objective number is defined in the Briefing.html file. After every objective is completed you'll have a set of variables (according to the example they're called objVar1, objVar2, objCar3,... but of course you can choose whatever name you want for variables) so you can write in the "end" trigger condition
objVar1 and objVar2 and objVar3 and...
which means that it triggers when every objective is done (that is, the corresponding variable is set to true). In this way the mission ends when every objective is completed.
5. You can do this in two ways. If you want the chopper to land and unload the unit it's carrying you can use "Transport unload" or "Unload". The first one works if the cargo units are not in the same group of the vehicle and need to be synchronized with a "Get out" waypoint linked to the cargo group leader. This means you have to put a "Tranport unload" waypoint for the chopper and place it at the landing zone and a "Get out" waypoint for the cargo group leader and place it near the previous waypoint and then syncronize them. If the cargo units are in the same group of the vehicle you just need to place a "Unload" waypoint for the vehicle at the landing zone. In both cases if you want the chopper to land exactly where you placed the waypoint you must place a H object or a Invisible H object (you can find them selecting "empty" or "void" side , don't recall the name right now, and then selecting "Object" in the class field).
The second way is to use the
land command but in this case the units in the cargo space will not get out automatically. (you can find docs here:
http://community.bistudio.com/wiki/land)
6. To write a briefing you must know the rules of .html language (but just the basic rules like what tags are and how you use them). To create a html document you can use notepad or download notepad++ which is free and highlights with colors the text tags and sections (very useful for large brieifngs). If you want to make a simple briefing then download ArmaEdit, it's a text editor that highlights arma/ofp script commands (useful to make scripts of any sort) and has also a wizard to create briefings. Also this link may be helpful:
http://www.flashpoint1985.com/docs/briefing.html