Im in germany. I bought the iPhone in the 1st quarter this year at a tmobile germany store, the Sim was with the iPhone. So T-Mobile Germany is the/one of the approved carriers in germany.
2. jailbreak, activate, unlock (you need the unlock because without it you cannot use your tmobile sim on it, specifically, tmobile usa right?)
3. jailbreak if you only want to install 3rd party apps
4. on 1.1.4, i say use installer.
Where are you? your post is very confusing because we don't know if you are in a country where tmobile is the approved carrier for the iphone? If tmobile is the authorized carrier for the iphone then answer to #2 is different.