Diciduous forests vary too much to apply one number. However, there are usually several (perhaps anywhere from 10-1000?) species of tree depending on the region. Additionally there would be hundreds...
Oak and Maple Trees.
yes, a deciduous forest isn't just all leaf shedding trees but mainly are but there are some trees that stay the same all year long.
yes
Four seasons. Summer, Winter, Fall (Autumn), and Spring.