Hi!

Sorry for so stupid question, but we argue with friend, and both of us think he is absolutely right.

Player A plays tactical card, for example, "destroy target ally". This card goes to the chain.

Player B plays action of that ally, for example, "tap this ally to deal one damage to target ally". This action goes to the chain.

Player A plays tactical card, for example, another "destroy target ally", targeting same ally as at first time.

Can players play cards/actions this way? Or every action/tactical card must resolve first, and only then another player can play action/tactical cards?

It's correct to play it that way. Players take turns adding actions to the chain until both of them consecutively pass. Then the chain resolves, starting with the last action.

Does it mean the secondly played "destroy target ally" card kill the first played "destroy target ally" to?

If they both target the same unit, the one played last will resolve first and destroy that unit. When the other one tries to resolve later, it won't have a target anymore, so it's cancelled.

Just to make sure I get it correctly:

there is no point in playing the second "destroy target ally" card on the same target, because the first will destroy the ally, and the effect of the ally will trigger even if the ally is destroyed, as the effect is independent of its source once it is played.

(Of course, if this "destroy" was a Spell, and Player A has a card in play which triggers when a Spell is played, then there is a point in playing it - my question is narrowed on the situation in question.)

I guess Player A played the second "destroy" in order to prevent the ally to deal that damage. But its just aint the way. Only effect cancelling cards would help.

Do I get it correctly?

Yes, that's correct.