Is 2 lumens bright enough to light a walkway?

No. Two lumens is about as dim as solar lights get. Expect a faint glow that marks the edge of a path, not enough light to see your footing clearly.

How long does it stay lit at night?

Runtime depends on how much sun the panel gets. On a full day of direct sun, small solar stake lights like this typically run for several hours after dusk, less on cloudy days or in shade.

Does it turn on by itself?

Yes. Solar lights of this type use a light sensor, so they switch on at dusk and off in daylight without a switch.

Can it stay outside in rain and winter?

It is made for outdoor use, so rain is fine. Freezing temperatures shorten battery life, and heavy snow or ice can crack the plastic stake.

What do I need to set it up?

Just soft ground. Push the stake into soil or mulch where the panel gets direct sun, and let it charge for a full sunny day before expecting a night of light.

How does it compare with brighter solar path lights?

Brighter models put out tens of lumens and cast a visible pool of light. This one is for subtle marking only, so pick it for looks and simplicity, not brightness.