Flashback and cards without mana costs

[Aggro_zombies]

Let's say I have a Dralnu, Lich Lord in play and an Ancestral Vision in my graveyard (or any other spell without a mana cost). I know that if I remove an Ancestral Vision from the game with Mind's Desire, I can play it without paying its (nonexistent) mana cost, but is the same true for flashback?

1) Does it have Flashback :0:?

2) Can I play it using its flashback cost?

3) If not, how is this different than Mind's Desire? One is "Without paying its mana cost," but the other sets up an alternate cost.

4) For kicks, let's say I have Fist of Suns in play. Can I now play any mana costless spells in hand for :w::u::b::r::g: (such as Ancestral Vision)?

For reference, Fist of Suns' Oracle text reads:
You may pay :w::u::b::r::g: rather than pay the mana cost for spells that you play.

[Nihil Credo]

1) No. The mana cost of Ancestral Vision is {} (read that as "nonexisting" or something similar. I like "null", myself). This is a mana cost that cannot be paid.
Dralnu's effect says its flashback cost becomes equal to its mana cost as you play it. So Vision's flashback cost is {}.

2) You cannot pay its flashback cost, for the same reason that you cannot pay its mana cost. Therefore, you can't play it (unless you have some other effect that lets you play it without paying its mana cost).

3) It's exactly like you said. Mind's Desire says "Without paying its mana cost", so the {} isn't a problem because you don't have to pay it. Suspend works in the same way, after all. Dralnu or Recoup instead do look up the mana cost, and you end up with something that can't be paid.

4) Yes. "Rather than paying the mana cost", like "without paying its mana cost", absolves you from the need to pay {}.

[Aggro_zombies]

1) No. The mana cost of Ancestral Vision is {} (read that as "nonexisting" or something similar. I like "null", myself). This is a mana cost that cannot be paid.
Dralnu's effect says its flashback cost becomes equal to its mana cost as you play it. So Vision's flashback cost is {}.

2) You cannot pay its flashback cost, for the same reason that you cannot pay its mana cost. Therefore, you can't play it (unless you have some other effect that lets you play it without paying its mana cost).

3) It's exactly like you said. Mind's Desire says "Without paying its mana cost", so the {} isn't a problem because you don't have to pay it. Suspend works in the same way, after all. Dralnu or Recoup instead do look up the mana cost, and you end up with something that can't be paid.

4) Yes. "Rather than paying the mana cost", like "without paying its mana cost", absolves you from the need to pay {}.
...damn.

Thanks Nihil.