I do not remember the Mimic quest very well but to get the Mimic class, you need to complete the Death and Rebirth Questline you receive at level 60, here is a complete guide to the questline that you may follow: http://freetoplaymmorpgs.com/eden-eternal/dylan-gallops-eden-eternal-mimic-quest-skills This guide explains everything to get the Mimic class.
For the Dragon Knight Class Quest, you go to the Andrew V. Mine in the human/halfkin starter zone, Limestone Mountain. To pass the quest, you need to read the zone chats and use the appropriate skill it hints at. The Dragon Knight quest in the mine requires reading comprehension and is random so I can't tell you to do any combination of skills.
When it tells you to "dig harder" in a long paragraph use the first skill
When it says to "find, detect, or search" use the second skill
When there is a long paragraph that mentions "Blueberries" use the third skill
If there is anything else you need help with or if I did not explain well enough please let me know.