It is a bit flexible on the part of WADNR, but most campgrounds which are closed over the winter, or used as SnoParks, will open or revert to standard camping in April. This year, 2022, DNR says that they are opening Teanaway as conditions allow or by April 13. DNR's web site has a chart they keep updated about site openings and other details. https://www.dnr.wa.gov/campsites

Not sure. I think it depends on when the snow melts.

This year it is April 13!