Question: How did the streetcar, phone booths, and vending machines end up in the digiworld?
Answer: We are never told as to how they got there.
Answer: People who built the digital world most likely had them sent there. Gennai tells the kids in the last episode that the streetcar was from San Francisco, and he asked them to take it back for him.
Question: During a restaurant scene Drea deMatteo plays a hostess. She seats the Sopranos, but does not seem to know them. Was she picked to play Adriana after this episode?
Answer: Yup, just like Nicholas Lea was chosen to play Alex Krycek on the X-files after showing up on 1 episode as a different character.
Question: What is the name of the theme song of Roswell? I think it's something called "Here I am", or "I am what I am".
Answer: It's called "Here With Me", performed by Dido. It can be found on her album "No Angel".
Answer: Everybody including Angel saw her. After helping them and then being left alone to talk to Angel, Cordelia says that the Powers That Be let her come back one more time to help them. After Angel gets a call saying that she died, he realises that it was her spirit that was helping them the entire time.