Hello crosscountry runner!
I'll try to help as best as I can, okay?
1)For myself, I don't eat anything out of my normal foods or portions. I made a mistake eating a big dinner of pasta, chicken and vegetables because my coach wanted me to. Eat healthy, whole foods but don't overstuff yourself. Most important thing is to hydrate the day before your race.
On race day, I usually have a piece of fruit (Banana is a good choice.Orange juice or a little yogurt. Keep it lite.) I would not recommmend caffeine beverages a few minutes before you run. Due to possible stomach upset and nervous tension,
I 've see two team mates throw up during the race.
2) After a light to moderate warmup, our team would do a few strides (imagine a deer gracefully bouncing on the greens)Another would be to roll your ankles to insure their ROM. Double knot your shoe laces in case they become loose. Practice some visualization exercises the night before and on race day such as seeing yourself pass other runners one by one, sprinting to the finish line or pacing yourself evenly on a hill.
You can warm up the upper body with circling of your arms. Do shoulder some shoulder rolls too.
3) I would not stretch after a hard run. The body needs to cool down slowly by gently walking and relaxing. Do not bend over to stretch your hamstrings since your low back muscles might still tight from the run. Make sure you ease into your stretches for your calves, hamstrings and low back.I assume your coach has taught you about good racing form during uphills, flats and downhills.
4)Again eat something lite such as fruit after your run but when you become hungry later, then have a good brunch from the four food groups.
Anyways, here are my suggestions. Hope the weather is not too warm and would love to hear what your trails are like. Take care.