datasheet on page 13 states that the ADV7612 supports 36-bit 4:4:4 YCrCb, but the table 5 and 6 do not list this mode. Is it supported, how can it be activated?
It's going to be Table 6, 36-bit SDR 444, you will just need to set the output color space. See the hardware guide Table 41.
Table 41 is about audio
Sorry, was looking at older hardware guide. In that guide look at Table 43