1) Yes, I have successfully passed data using the dev board, although none of the statistics registers in UART updated, only when running stats_chk in the system console when running the tcl scripts.
2) I set up local loopback by writing x803B to command config reg, but I still do not see any status registers changing.
Also tested a form of PHY loopback test by directly connecting the RGMII rx signal to the RGMII tx signal in the MAX10 and using signal tap to verify that they were the same. So it looks like our PHY does
3) I should have mentioned that the PHYs are programmed via hardware strapping for the correct modes, RGMII to copper and RGMII to 1000Base-X and most of the configuration is done by that. I am able to write to the PHY, for example to set the activity and data LED signals to the proper mode, but all other settings should be done via the strapping.