Determining eligibility to accept a quest based on ID.
 

Is it possible to determine if a user is eligible to accept a quest based on the ID? I'm specifically looking for chain-quest pre-requisites, but one that determines the outcome based on character level would be cool too.

An example of this (In classic WoW) would be Quest 804, which requires that the user had completed Quest 790 to accept.

Yes, it's possible. I'll go further in detail when I get home.

That would be greatly appreciated, I've been destroying the wowwiki on fandom and I have yet to come across it.

You might want to download the addon Grail. It is a quest database and you can use its functions to determine if you can accept a quest based on its ID. You can also find out the reasons why you cannot (like wrong faction, not high enough level, not enough rep, missing prerequisite, etc.). If you want, you can also use the addon Wholly which will give you a visual representation of this information as well as adding map pins for quest givers, etc.