What direction does the earth rotate during vernal equinox?
As usual. The Earth's equator and its orbital plane have two common points. At an equinox, these are on Sun-Earth line. When the diameter joining these points is perpendicular, it is a solstice
The equator and ecliptic intersect along a diameter of equator. This diameter on the ecliptic rotates about the center of Earth once in a year in the ecliptic. Earth rotation (spin or orbital) is as usual.This is my brief explanation.