If you did the Romeo and Juliet quest its that same house.
Yes, every few months Runescape pumps out a new quest ranging from beginner (very easy) to Special (practically impossible to complete without dying).
It's currently not possible to undo a quest in RuneScape.
Rune mechanics
The legends quest on runescape is not gone, I suggest that you check again.
You will have to find out on the day, like everyone else.
its not a certein level that you need you have to complete all the quests if you do do this and a new quest comes out you cant wear it until you do that quest
It is a quest, that introduces a new potion into the game, and is a prerequisite for other quests.
A quest on Runescape is an adventure that puts you in a conflict, you solve it and you get rewards like money, skill experience points, quest points, and items.
It is in a way for a sort-of new player, but it does get easier, there are guides out there that show you what to expect.
If you quit runescape...
There are many websites where one can get advice on completing a Runescape quest. The Runescape website itself offers advice as does the website Tip.It.