Kestia, the Cultivator

The phrase "you control" applies to both "enchanted creature" and "enchantment creature." That is, Kestia's ability triggers when an enchanted creature you control attacks, not any player's enchanted creature.

Bestow is an alternative cost to cast the spell with bestow. It can't be combined with other alternative costs, such as casting a spell "without paying its mana cost."

Unlike other Auras, an Aura with bestow isn't put into its owner's graveyard if the enchanted creature leaves the battlefield or becomes an illegal creature for the Aura to enchant. Rather, the effect making it an Aura ends, it loses enchant creature, and it remains on the battlefield as an enchantment creature. It can attack (and its abilities can be activated, if it has any) on the turn it becomes unattached if it's been under your control continuously, even as an Aura, since your most recent turn began.

If an enchanted enchantment creature attacks, you draw only one card for it.

To determine the total cost of a spell, start with the mana cost or alternative cost (such as a bestow cost) you're paying, add any cost increases, then apply any cost reductions. The mana value of the spell remains unchanged, no matter what the total cost to cast it was.

Auras attached to a creature don't become tapped when the creature becomes tapped. Except in some rare cases, an Aura with bestow remains untapped when it becomes unattached and becomes a creature.