When can you burn Spell of life for its effect?

Spell of Life

+1 stealth action.
Put this card in play. Only one Spell of Life may be played each turn. You may burn five Spells of Life to put up to five vampires from your uncontrolled region in play. Each represents a unique mummy ally with life equal to capacity, 1 bleed and 2 strength who can enter combat with a minion as a Ⓓ action.

When are you able to burn the spells of life? Only on play, if playing the fifths or later spell, or anytime? (for example during your influence phase after drawing new vampires)

Bonus question: Can they act on the same Turn as they enter play, since they are not recruited?

There is no timing specified, so you can do it any time you have the impulse.

Since the mummies are put into play and not recruited, they can act immediately (if you created them in your turn). See rulebook 6.1.5.