Hi Soumya-
1) The evaluation board for AD9625 does have support for 3.3V on DVDD_IO & SPI_DVDD_IO. The datasheet for AD9625 will only specify 2.4 to 2.6V for these domains. The 3.3V support may be added in the future, but will not be reflected in the released datasheet at this time.
2) The datasheet will show 1.26Vmin and 1.32V max for AVDD1, DRVDD1 & DVDD1. This is the final characterized operating range for the release of AD9625.
Your use of 1.3V and 2.5V respectively will be correct for the operating range of the AD9625.
Thanks,
Ian Beavers