#1: p42 Major Actions: "Astral Projection"
#2: You'd have to assense it, yes. Doesn't have to be from the Astral, you could just be astrally perceiving. If you look at the Assensing table on p159, you see 2 hits is enough to detect the type of focus, while with 4 hits you can even pinpoint its exact Force
#3: Spirits have Sapience, so they can do things on their own. However, language it probably depends on the GM. Though it is quite reasonable to assume a Spirit can at least somewhat communicate in our language. (In fact in previous editions Free Spirits did not explicitly receive language skills, so apparently something's implied there.) But if it's opposing you, chances are it won't talk to you but try to fulfill its services instead. If it's a Free spirit or a Wild spirit, it's more likely to cooperate/communicate. As for whether a spirit is willing to answer your questions, that's entirely up to them.