Can DELTA/RIVER be charged and used to power a device at the same time?

All EcoFlow power stations can be charged using AC or DC input and also used to run devices at the same time (using AC or DC output). You can charge and discharge power stations at the same time.

Does DELTA/RIVER work with 3 prong devices?

 EcoFlow DELTA/RIVER AC output supports a 3-prong plug. There are small holes in the middle between the AC output ports. Those are for the third prong. In order to meet the UL2743 standard, EcoFlow power stations’ sockets are not grounded and we didn't do grounding-free optimization. If you want to charge your appliances with a ground line for safety consideration, it is recommended to do a DIY adapter or purchase one to simulate grounding.

https://ecoflowtechhelp.zendesk.com/