Ian Carfax and Rötschreck

Ian Carfax

Camarilla Tremere Justicar: Once each turn after a combat involving Ian ends, he can unlock if the opposing minion is not ready. +1 intercept.

Rötschreck

Master: out-of-turn. Frenzy.
Put this card on a vampire when an opposing minion attempts to inflict aggravated damage on him or her, whether the damage would be successfully inflicted or not. Combat ends. This vampire is locked and sent to torpor. This vampire does not unlock as normal. During this vampire's next unlock phase, burn this card.

Question: if opposing vampire going to torpor after Rötschreck ,will Ian Carfax text still apply?

yes, Ian text only ask if the opposing minion is ready or not, if not he can unlock

No. You go to torpor with Rotshreck after combat.

Would be good to get an official ruling on when the below mentioned time window closes... is it limited to be within the action where the combat occurred or does it last till the end of the player's turn

"Once each turn after a combat"

"after" is always immediately after and is ordered in the window for all immediately after effects based on impulse.