1) Which cryptocurrency pairs can I currently exchange via BitShares?
6) Can I exchange crypto for crypto directly or do I always have to buy BitShares unit?
7) If no, why can't you make it so I can exchange crypto for crypto directly?
This page lists the assets that currently exist in BitShares:
http://cryptofresh.com/assetsYou trade any of these assets against any other, but most of these markets are empty.
You cannot trade any (crypto)currencies directly. Instead, there are a variety of BitShares assets that represent external currencies, most importantly BTC and various fiat currencies. There are currently two different types of representative assets:
* SmartCoins aka Market-Pegged Assets - these are loosely coupled to the external currency they represent, see Question 9
* certain user-issued assets - these work like IOUs and they are issued by an external (centralized) entity, that entity guarantees that the IOUs are redeemable for the asset they represent. The most widely used IOUs are probably those from OpenLedger, for example OPEN.BTC etc.
9) How can a censorship resistant, decentrilised exchange like BitShares determine the USDT tied value? How can it be done? How technically blockchain can determine what is the EUR or USD value? It has to take data from someplace, right? So if it is not centralised, how is this data received to the blockchain?
SmartCoins in BitShares rely on an external "price feed". The owner or issuer of a SmartCoin can specify a number of trusted users who are allowed to publish the external price of the token against its underlying asset. Typically, SmartCoins are owned by the committee, and the price feed is published by the witnesses (who also sign the blocks).