I built a picnic table out of this redwood 10 years ago or so and it is still in great shape.
These boards do not require batteries to operate.
Check with your local building authority.It depends upon what roofing material will be used, the spacing O/C, there are too many variables to answer your question completely. You may also need to factor in snow loads??
YES YOU CAN USE IT ON DECKS AS LONG YPU PRIME IT AND PAINT IT BEFORE INSTALLATION
The current topic is about DRIED lumber, not TREATED lumber. This is just dried. Treated lumber takes on a green or brown appearance.
They may have been out, but I frequent 5 different Home Depots, in different states, and they ALWAYS have 2x6s in stock .I'd look again.