Kalamax, the Stormsire

You can't choose to pay any additional costs for the copy created by Kalamax's first ability. However, effects based on any additional costs that were paid for the original spell are copied as though those same costs were paid for the copy too.

If the spell that's copied has damage divided as it was cast, the division can't be changed, although the targets receiving that damage still can. The same is true of spells that distribute counters.

Kalamax's first ability considers the entire turn. If you cast an instant spell before Kalamax becomes tapped, its first ability won't trigger when you cast your second.