the sun is directly above the equator. The vernal equinox occurs on this day.
yes
The beginning of Spring in the northern hemisphere is the beginning of Autumn (Fall) in the southern one.
yes
vernal
No. Easter is a Christian festival that happens to be at the start of spring (in the northern hemisphere)
The Spring Equinox. This is the day that both both daytime and nighttime are functioning in the exact same span of time. (IE. Daytime = 12 hours, Nighttime = 12 hours = Spring Equinox.)
The spring equinox marks the beginning of spring. This is a date where night and day are exactly equal. In the northern hemisphere, this day falls on or around March 21st. In the southern hemisphere, this day falls on or around September 21st.
That happens when at the March equinox - usually the 20th or 21st of March. This is the beginning of spring in the northern hemisphere, or the beginning of autumn (fall) in the southern hemisphere.
When it's autumn in the southern hemisphere, it is spring in the northern hemisphere.
In the northern hemisphere, the first half or so, is summer. On the 22nd it becomes fall. In the southern hemisphere, the first half or so, is winter. On the 22nd it becomes autumn.
That depends on where you mean when you say "here". If it is anywhere in the northern hemisphere, then the answer is autumn. If it is somewhere in the southern hemisphere, then the answer is spring.
The vernal equinox marks the beginning of spring in the Northern Hemisphere.