Line of Fire from 3rd level elevation to 1st level elevation and vice versa.

How does that work? Possible...no...

Thanks.

It depends on a lot of factors. Is there any blocking terrain between the two? Is there any elevated terrain with a higher elevation than level 1? Is the character on level 1 a giant or colossal?

The only part of this that matters is the Giant/Colossal question. When ever a Line of Fire Crosses multiple Elevations that Line of Fire is blocked. A Giant/Colossal though are always considered to be at the highest Elevation so if the character drawing the line of fire were drawing that line of fire from Elevation 3 to a Giant on Elevation 1, that would be perfectly legal provided there was no Blocking Terrain Between them.

If the character drawing the Line of Fire was on Elevation 1 and was not a Giant/Colossal then it could not draw a Line of Fire to Elevation 3 and Vise Versa.

I say this because there are no points on the map where the Elevation goes from 1 to 3 without crossing 2 and vise versa. If the Elevation did go from 1 to 3 without crossing 2 then you could draw that line of fire.