What is the difference between quest types in MH4U?

I find a little confusing that the game has so many quest types, and I can't get what are each type of quest for.
There are Caravan quests, which as it seems, are the quests that progress on the game story, and this one is pretty straight forward. There are also those quests at the Gathering Hall: Low Rank Quests High Rank Quests Arena Quests Challenge Quests Guild Quests Event Quests Expeditions And when I talk to the Palico in my house, there is also an "Episode Selection".
Could someone explain to me what are each of these for, and why would I want to do a quest of that type?
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What are the guild quest in MH4U?
If you fulfill certain conditions during an Expedition, such as slay the specified large monster, the Guild will give you clearance to take on special Quests. These are called Guild Quests, and they can be registered via the menu and then selected from the Gathering Hall's Quest Counter.Is MH4U harder than MH3U?
I'm still working through the Caravan quests right now too, but it feels like MH4U is much more difficult than MH3U was. Even at LR I've noticed a LOT of monster behavior and moves that you would only find at HR and G-Rank in 3U, or at the very least weren't nearly as common.Does MH4U have G rank?
Once you complete the HR 8 Urgent Quest, you become G Rank, which opens up the hardest difficulty of monsters in the game, along with the best gear. You partake of G Rank quests in the Elder Hall, not the Gathering Hall. You will not even be allowed to enter the Elder Hall if you are not G Rank.How to get guild quest MH4U?
Every time you finish one of your free jaunts in the Everwood, there's a chance that it will unlock a guild quest. To boost your chances, you'll want to take down multiple monsters and also pick up the shiny drops they leave on the ground after you punish them hard via mounting or by breaking body parts.[MH4U] Monster Hunter 4 Ultimate Custom Quest Tutorial
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