Yom Tov

According to the Talmud in Masechet Pesachim, there is a mitzvah to drink wine on Yom Tov for Simchah Yom Tov. My question is, can grape juice substitute for wine on Yom Tov?

According to Halacha, it is permissible for Jews to recite havdalah early before Shabbat ends (although it’s recommend to do so in extenuating circumstances). My question is, does the same rule apply to Yom tov?

In Halacha there is a mitzvah for a husband to give his wife a gift, especially clothes, on Yom Tov. My question is, can a husband fulfill this mitzvah with regifting his wife something he had been given previously. Or does he have an obligation to buy it himself to fulfill the commandment?

If Shabbat is the most important Jewish holiday, more important than Yom Tov, then why does the Yom Tov liturgy take precedence over that of Shabbat when the two coincide? Why is it that the main body of the Amidah text is that of Yom Tov, with some Shabbat additions, and not the other way around?