I would assume in about a week. First the Rhee Event will have to run out. Sometime towards the end of this month I'd say

They are used for the kitten stuck in the grass

How about putting up more decorations? You can also use the speedboat keys which you can find in the treasure hunters house or win in competitions

Upgrade your Pier, put down more decorations

I get them mostly from the Treasure hunters house boxes or when I finish achievements they might pop up in a reward box

put something in your warehouse and then something else, once the slots inside your warehouse are full it will automatically prompt you to expand your Warehouse.

Play the game Search the waves!

Bronze keys ARE for chests, now there are also Boat keys, which look similar but are not the same. You might not have enough Bronze keys to open a chest? You can find the Bronze Keys at Events or the Treasure Hunters House

seeds for what?

You find those in the foggy areas on trees, you could even follow the birds and wait till they land on a tree and then click on them

What part of the quest are you on so we can better help you out. It gives you specific instructions but if you can let us know what exactly the problem is for you its easier to help out