Is there any dac that have 24 bit precision at 40khz??
No. The best @amirm ever measured, IIRC, is -122 dBFS in the Okto DAC8, or about 20.3 bits. Even @amirm's laboratory-grade state-of-the-art audio analyser wouldn't be able to measure 24 bits. My understanding is that analog electronics can't do much better than 20 bits because you start running into fundamental limits such as Johnson noise in resistors.
Yes but is there a precision in the frequency ? Is this always the same for the whole frequency range ?
Yes, because the DAC is driven by a single clock. As far as I know, there is no reason to believe the relative frequency error would be dependent on the frequency itself.