Yes, ranged flyers can attack ground creatures they share a zone with, ignoring minimum range.
A creature cannot gain flying during an attack. You can reveal Eagle Wings at the end of any attack step, but it will not help you.
My understanding is that you can, exactly the same way you can reveal Divine Intervention to avoid an attack.
"A spell fails and is canceled, if either of the following occur before the Resolve Spell Step:
1. The target of the spell is no longer a legal target, or
2. The caster or target of the spell moves (e.g. by being Pushed or Teleported away), even if the
move was to a location where the spell was still in range. (In the case of a Teleport, this applies
even if the teleport was into the same zone).
Similarly, an attack fails and is canceled, if either of the following occur before the Apply Damage and
Effects step of an attack :
1. The target of the attack is no longer a legal target, or
2. The source or target of the attack moves (e.g. by being Pushed or Teleported away), even if the
move was to a location where the spell was still in range. (In the case of a Teleport, this applies
even if the teleport was into the same zone).
The most common way these can happen is through Divine Intervention"