Here a list of all the quest you can repeat infinity after all the main quest is done.
Some quest requires you to advance the main quest of that faction, and other are chain quest with only the last one being repeatable.
Note that it won't allow you to go above A grade in stats and 4 in magics.

Forgotten Fountain

• Gnosis Shards ( x 8 )
  
• + 12500 xp
  
• +2 Relics cap Cultist
  
• +2 Relics cap Air
  
• +2 Relics cap Water

Soul Bargainer

• Need Level 6 or more
  
• Gain "Tainted Aura"

Lost Soul

• Need "Tainted Aura"
  
• + 12500 xp
  
• Gain "Corrupted Aura"

Dungeon Crawl

• Need Power B+ or less
  
• Need Level 12 or more
  
• + 12500 xp
  
• + 1 Power

Soul of Magic

• Air 3 or lower
  
• + 12500 xp
  
• +1 Air Cap
  
• OR
  
• Water 3 or lower
  
• + 12500 xp
  
• +1 Water Cap

Comfort Food

• Trade up to 15
  
• Voidcap ( x 1 )
  
• To
  
• Random Spices ( x 45 )

Orepit Offerings

• Gnosis Shards ( x 8 )
  
• + 12500 xp
  
• +2 Relics cap Tranquility
  
• +2 Relics cap Temperance
  
• +2 Relics cap Diligence
  
• +2 Relics cap Exuberance

As Above, So Below

• Gnosis Shards ( x 8 )
  
• + 12500 xp
  
• +2 cap Relics Shattered
  
• +2 cap Relics Earth

Holy Carving

• Earth 3 or lower
  
• + 12500 xp
  
• +1 Earth Cap

Endurance Test

• Need Level 6 or more
  
• Gain "Girded for Battle" 25% hp as armor

Extreme Competition

• Need "Girded for Battle"
  
• Gain "Armored for Battle" 50% hp as armor

Flavorless Feasts

• + 12500 xp
  
• Trade up to 10
  
• Gutberry ( x 100 )
  
• Bitterice ( x 100 )
  
• To
  
• Stone ( x 125 )
  
• Iron ( x 125 )
  
• Sculpstone ( x 100 )
  
• Ignium ( x 50 )

Training Regiment

• Need Level 12 or more
  
• Need HP B+ or less
  
• + 12500 xp
  
• + 1 HP Grade

Occult Lessons

• Dark 3 or lower
  
• + 12500 xp
  
• +1 Dark Cap

Diligence Reverence

• Gnosis Shards ( x 8 )
  
• + 12500 xp
  
• +2 Relics cap Vivified
  
• +2 Relics cap Dark
  
• +2 Relics cap Diligence

Full Immunity

• Need Level 6 or more
  
• Not Vivified
  
• + 12500 xp
  
• Gain "Pain Immune"

Forgotten Altar

• Gnosis Shards ( x 8 )
  
• + 12500 xp
  
• +2 Relics cap Humain
  
• +2 Relics cap Lighting
  
• +2 Relics cap Fire

Potion and Meals

• + 12500 xp
  
• Trade up to 3
  
• Sunshadow Nut ( x 6 )
  
• Bristle Cone ( x 3 )
  
• Sweetleaf Nut ( x 2 )
  
• Runewood Nut ( x 1 )
  
• To
  
• Potion of Perfect Rejuvenation ( x 5 )
  
• Potion of Perfect Recharging ( x 5 )
  
• Random Meals ( x 3 )

Xathar's Exploits

• Need Mana B+ or less
  
• + 12500 xp
  
• +1 Mana Grade

Volume III Shocking Heights

• Lighting 3 or lower
  
• + 12500 xp
  
• +1 Lighting Cap

Look Up My Sleeve

• Need Level 6 or more
  
• + 12500 xp
  
• Gain "Potion Up A Sleeve" +1 potion slot

Abracadabra

• Need "Potion Up A Sleeve"
  
• Gain "Potion Up Another Sleeve" +1 potion slot

Never Ending Rat

• + 12500 xp
  
• Trade up to 20
  
• Wood ( x 10 )
  
• Stone ( x 10 )
  
• Wyrmweed Pod ( x 10 )
  
• To
  
• Sinew ( x 5 )
  
• Brain ( x 1 )
  
• Eyeball ( x 2 )
  
• Etcplasm ( x 2 )

Tranquil Progenitor

• Gnosis Shards ( x 8 )
  
• + 12500 xp
  
• +2 Relics cap Wolfkin
  
• +2 Relics cap Nature
  
• +2 Relics cap Tranquility

Ecstatic Educators

• Fire 3 or lower
  
• + 12500 xp
  
• +1 Fire Cap
  
• OR
  
• Nature 3 or lower
  
• + 12500 xp
  
• +1 Nature Cap

Relentless Kudzu

• + 12500 xp
  
• Trade up to 10
  
• Iron ( x 20 )
  
• To
  
• Thorntooth ( x 10 )
  
• Fungal Helix ( x 10 )
  
• Anemone Cell ( x 10 )
  
• OR
  
• 4 mages total Nature + Water
  
• Thorntooth ( x 5 )
  
• Fungal Helix ( x 4 )
  
• Anemone Cell ( x 4 )

Impossible Love In Trouble

• Need Level 12 or more
  
• Need Speed B+ or less
  
• + 12500 xp
  
• + 1 Speed Grade

I edit the game files to make the quest 10 times faster and play normally until I was confident that I got all the quest, so I should have everything.
here if you went to play:
Steam\steamapps\common\MindOverMagic\mindovermagic_Data\StreamingAssets\Quests