Your Mom... just jks... I personally think frost dragon bones.
Yes. If someone have reported when you botted. They make take a while to analyze the pattern you or your bot's mouse clicks.
The most expensive item on RuneScape is the Christmas Cracker. But the people in the beginning of runescape opened most of them for the partyhats inside them so there are only a few left. There are some left, or they wouldn't be listed on the Grand Exchange Database.
The most expensive item in Runescape is a Christmas Cracker. I would say the price of one of these would be around 8-10b. Sorry for not an exact price but I don't know the exact figure :P
Blue partyhat costing 2100M
Currently, at over 2,000,000,000 coins, is the White Partyhat.
No.
Just search for 'Runescape item ID database' and you'll find multiple services to search for item ID's.
Water
There is no NPC, place, or item in RuneScape called "Kela."
No.
the most expensive: blue partyhat the most useful combat weapon: corrupt dragon scimitar
bronze dagger