All 3 are great things for health.
Exercising at the end of fasting window works great for me.
I don’t do cold adaptation stuff myself, but the science is really positive on the health benefits.
I’d say go for it.
It will have no effect at all on health benefits. The benefits of IF come from sustained periods of keeping insulin low. Exercising briefly and taking a cold shower right before eating don’t do anything to affect insulin long-term.
Now, it likely won’t do any harm, either (edit: as long as you aren’t exercising to a point where you feel bad). So if you like the feeling of having an exercise/cold shower ritual to mark the end of your fast, go right ahead. Just be aware that it’s a psychological effect, not physical.
(Also — “combo-wombo”?)