Superiority in lineage

Q:

1. My question is regarding the rule in Islam that commands Muslims to choose their caliph (khalifah) from among the tribe of Quraysh. The question here rises that how can Islam limit leadership to Quraysh and create a concept of Qurayshi , Non-Qurayshi.

2. Secondly I have read on another website that Arab Muslims who's piety is superior to non Arab Muslims piety in “general terms” as they are better in linage and descent. This again is a very irrational mentality. Clarify the following.

Selling gold online

Q: I intend to begin online precious metals trading (buying and selling gold online for example), and I read the mas’alah that “purchasing gold online in exchange of money” is permissible. Can you please explain what this means?

Playing a game with a halloween theme

Q: I play a game where you can decorate a room with furniture for diffrent kinds of houses around the world. On this game there recently came out to design a room for a bewitched/haunted house and you can get extra points. It doesn't really exist and they put that theme up because of halloween. I thought its haraam to design it but did non the less. Is it kufar what I have done. The one house they said was haunted and the other they said a lady built the house to appease her husbands ghost (I read that part only after I designed it and got points).