This is a simple AddOn that let you know if you have already completed a quest or questline by providing it's ID.
Result(s) will be shown in default chatframe. (For some hudge questline, it can spam a little so :) )
All ID's can be found on Wowhead
Use /qc or /questchecker to open InterfaceOptionsFrame
THIS IS A WORK IN PROGRESS
If you have an 'unknow Quest Title', then request again. It happen for some questlines actually. working on it.
If you encounter bugs or have suggestions let me know below !