Either I'm reading it wrong or there's a typo there. If you are in Delhi, you won't then fly AI into it. Or did you just fly from somewhere into it?

Some AI flights indeed do not have a J cabin. I assume this one did.

Refund should be based on difference in price although I assume you'll get the miles and got priority services including the lounge?

What was the cost difference from this flight with an issue from J to Y?