Together they're called Timmy and the Lords of the Underworld.

Yes it is. However, you have to own Rock Band 1 in order to export it into Rock Band 2. Importing almost all Songs from Rock band 1 will cost you only 400 MS Points or 5 Dollars / Euro, dpending on the system you use.

To answer the question precisely: No, Timmy & the Lords of the underworld is not featured in Rock Band 2, but in Rock Band 1.

The band Styx, which was formed in 1961 was originally known as The Tradewinds. In 1965 the band changed the name to TW4 after a band called The Trade Winds broke nationally. Finally, after signing to Wooden Nickel Records in 1972, the name was officially changed to Styx. Dennis Deyoung has said the reason that it was chosen was because it was the only name that none of the members hated.

No I don't think so but you can get Timmy and The Lords Of The Underworld on Rock Band

Hades' Underworld is called The Underworld.