Please see:
https://ez.analog.com/message/149912#149912
1. GPO line status is as configured when powered up and transitioned into SLEEP state. After that GPO configuration settings are retained when going back to SLEEP mode.
2. SPI works in this mode. AUXADC will not work because all clocks in the chip are turned off in this state. You may be able to read a stored output value from a completed A/D conversion but that probably will not be useful to you.