The source for the melacha of transferring between domains on shabbos, connection to Moshe telling the nation to stop contributing donations to the mishkan
The prohibition of milking animals on Shabbat, applications to nursing mothers on Shabbat and milking cows in Israel where no gentiles are able to assist
One violation of Shabbos for an action that combines multiple potential violations, application to how far one may go in violating shabbat for a severely I'll person
Moshe added a day to preparing for the Torah on his own initiative- why Hashem agreed, and what it means that Moshe did this without Hashem telling him