Sorry, I cannot answer your first question.
Let me try to answer your 2nd question la ^^.
I think 修葉 is like hair cut, its a way to make your plant prettier. Of cause, a person/plant will not die if he/she/it doesn't get a hair cut. However, because the older or the smaller leafs at the bottom also consumes energy, 修葉 also means that more energy can be given to the new growth rather than keeping the old/yellow leafs alive. So I'd say that 修葉 also help to keep your plant healthy |