You must pay all costs when casting a spell this way.

If you play a land or cast a permanent spell from your graveyard using another permission, it won't count as the "once during each of your turns" for Kagha's effect.

You must follow the normal timing rules of the card you play from your graveyard.

Once you begin to cast the spell, losing control of Kagha won't affect it. You can finish casting it as normal.

If you play a land or cast a permanent spell from your graveyard via Kagha, and then have a new Kagha come under your control in the same turn, you may do so again that turn.