I have 2 x Casstelan of the Rock in play. I play a Lannister Location... How many characters I can kneel w/o attachments?

In the same round i play Die for Your King. Can I or not?

I just dont get it with this Limited Response...

It's easy: you can trigger Castellan of the Rock's ability OR play Kill for Your King! once each round.

Limit 1 Limited Response per Round means that you can trigger one of those responses each round. You can kneel one character without attachments or kill one character without a military icon. You can't do both in the same round.

Even more generally:

You personally can only trigger one effect with the "Limited Response" label each round. It doesn't matter how many different cards or different card titles you have; you can only trigger one effect that says "Limited Response" each round.