I remember my brother saying something about that...so my answer is yes but I'm not 100% sure
Yes, 20 is the highest level, alongside the fact you can only have up to 10 gold although you have infinite time on a trial account.
Yes.
No, once a trial account has been upgraded to a full account, you can not go back to using it as a trial account. If you want to do another trial account, then you need to sign up for a whole new one.
Go to the official site linked below. Create an account. Add WoW or a WoW trial to your list of games. Download client. Log on with your account, and create your character.
If you have the full game downloaded into your computer, no. All you have to do is make the trial account and when it says to download it dont, and just get on your trial account.
Yes I would believe so.
A trial account itself is not the issue, it's the installed program (client). Once you have that installed, and you have made an account with a private server, it will work regardless of you also having a trial account at Battle.net.
Technically, yes, but it would be better to download the whole thing if you have a regular wow account. The trial client is a streaming client, meaning that not everything is on your computer. It will be a lot slower, laggy, and things will take even longer than they normally do to load.
get to level 55 on a trial and download wow wrath of lich king trial
No. During the trial you are limited to level 20, which is not high enough to have a dragon/drake mount.
Yes, you can use any addons that a full account can use. There is no limit.
There are trial accounts that allow you to play for 10 days to try WoW out but that's it.
Yes, you should be able to play the test realm/client using a trial account.