What is Soma? Is it a drink or a metaphor for spiritual bliss or both?

Question

The whole Mandala 9 of Rig-Veda is devoted to the Soma. My question set is as follows.

1. What is Soma? What is its importance?
2. Are there both interior as well as exterior somas? I've read about interior somas which could be formed via yoga at ajna chakra, though I don't know of any scriptural references of interior somas.
3. Do we still have methods to prepare external somas? (It's evident from sculptures found in Indus Valley civilization that (external) Somas could be prepared)

_{Related: Which rituals need Soma? If the Soma plant is extinct, is there any substitute for it?}