Touch of Clarity and Fast Reaction is posible to play with locked minion?

I corrected your questions to make them more understandable.

beslin wrote:

1) A vampire play an action card requiring Dominate (or Presence). Can a LOCKED reacting vampire play a wake card (for instance On the Qui Vive) and Touch of Clarity to cancel the action card ?

Yes. Wake cards can be played in the "as played" window.

beslin wrote:

If I can, can I play both of these cards before the vampire plays a Seduction (or any card that can be played when an action is announced)?

You are obliged too, since cancelling a card happens before replacing that card, and "as the action is announced" are played later.

beslin wrote:

What is the right way to play these card to avoid problems ? Do you need to say to the acting player "stop, I will cancel this"?

The right sequence is:
a) acting player locks his vampire and plays the action cards.
b) you play a wake*
c) you replace the wake
d) you play a Touch of Clarity*
e) you replace the Touch of Clarity
f) the acting vampire is not locked (unlock him if he was unlocked before announcing the action) and the acting player replaces the action card.

* another player could also cancel your cards at that point, but I'll keep it simple.

If the acting player marks a pause at step a) to allow players to cancel his action card, then there should be no problem.
If the acting player plays his action card, replaces it and plays a Seduction (or even worse, as I see it played sometimes, both the action cards and the Seduction at the same time, before replacing both), all of that before** you can cancel the action card, then you have to stop him, revert back to when the action cards was played, and then proceed with the cancellation step, even if in the end, you don't cancel his card***.

** of course, it's always hard to prove there was enough time to allow the card to be cancelled. Still, most of the time, you should be allowed to roll back to when the card was played, unless the move was clearly a trick to know if the acting player had a Seduction in hand or not (up to the judge to decide).

*** for instance, your predator plays a Govern the Unaligned at superior, and you want to know if it is to gain pool by transferring back, or to bring out a new vampire (in which case you'd cancel it).

beslin wrote:

2) After combat between an acting minion and a blocking minion you control, can you play any wake cards with a LOCKED vampire and Fast Reaction to enter combat with acting minion.

Yes.