Preparing for Shabbat

On which day may one start wishing "Shabbat Shalom"?

When we make early Shabbat, is it better, when nighttime falls, to recite Kri’at Shema and sefirat ha’omer during the meal or to wait until after the meal?

I read that one should not throw directly into the garbage mitzva-related objects. Should I wrap in plastic the leftover shell and wax residue from “tea light” Shabbat candles?

After Shabbos began, I noticed that I had forgotten to light one of my candles. Must I light an additional candle in the future? “I was unable to light my Shabbos lights because of circumstances beyond my control. Must I begin lighting an additional candle every week in the future?

Should single men in Yerushalayim light 40 minutes before sunset like women do?

What Halachic principle is, strangely, named after a thief?

We forgot to plug in our hot plate, and so we asked our child (9 years old) to plug it in 11 minutes after sunset. We second-guessed ourselves in the morning. Was it permitted? If not, could we have used the hot plate then and benefitted from the food that was on it?

I am a man living alone. Last week, I forgot to light Shabbat candles. Must I light an extra one from now on?