Terraforming Mars: Prelude 2

No — some Prelude cards have actions or effects and "work like blue cards," but the rulebook explicitly states that neither corporations nor preludes ever count as blue cards (they don't count toward milestones or awards). (page 2)

Yes — preludes that show actions or effects function like blue cards, so their actions/effects operate as written; however, the card still does not count as a blue card for counting purposes. (page 2)

All preludes and corporations discarded in setup or during the game are placed face down in their respective discard piles, and if you run out of cards you shuffle the discard pile to form a new deck. (page 3)

If you draw a Prelude that requires an expansion you aren't using, discard it and draw a new card; the setup note also advises making sure you only play with the correct cards. (page 2)

If you reveal a Prelude you cannot play (cannot perform all its effects), you must reveal and discard it and you receive 15 M€ as a refund. (page 3)

Normally you choose from 2 corporations and 4 preludes at setup; the Variant: Extended Start lets you choose from 3 corporations and 6 preludes instead. (page 3)