It was Kaiser Wilhelm II (Germany) in August 1914. He wanted to assure the soldiers and the society that the war which was coming (now we know it was the WW I) wasn't going to be a long one (sadly, it didn't work that way).
dead leaves fallen under trees form a layer of DUFF which protects the ground from moisture evaporation
The person whose ground they land on.
This is best carried out when the leaves have fallen. With Evergreens do it in the early Spring.
I'm British and neither I nor anyone I know does anything with apple trees at Christmas. The apples have been eaten and its leaves have fallen long before Christmas.
Ladybirds sleep underneath fallen leaves and gaps in trees.
If the season is Autumn or Fall then the effect is much raking of leaves.
Trees can be deciduous or evergreen. Evergreen trees have leaves all the year round. Deciduous trees have leaves which die and fall off in autumn, then regrow in spring. You can find out if a tree is deciduous by waiting for autumn/winter, and seeing if its leaves have died and fallen off.
Yes
fallen leaves decay and make the soil rich with organic matter
fallen leaves decay and make the soil rich with organic matter
early spring when its not too hot and make sure it is irrigated
When dormant .After the leaves have fallen.