FlytrapCare Carnivorous Plant Forums

In nature the flytrap can choose what it consumes...just whatever happens to walk across the leaf and trip the triggers. I haven't done a lot of feeding, but my understanding is to feed only food that is no larger than 1/3 the size of the trap and only feed a couple of traps at a time. Once a week or every couple of weeks should be plenty. And, I've seen it recommended to feed the same trap each time. So, as long as you're not overfeeding the plant it should be fine to feed a small, just opened trap but the plant would probably get more nutrition by feeding a larger trap (and thus a larger food item). Just my thoughts...

If the trap is open, the plant is open for business, and it can feed/you can feed it. The issue you'll find with feeding one that small is that it can be very easily be given too big of a meal, and it'll rot before being digested. Just let it catch its own food.
In my experience, just keep them outside, keep them moist, and they'll take care of themselves in regards to food. In the height of the season, my flytraps will be 80+% closed/digesting meals, even the little ones.

It can, and you want to try to lessen the likelihood of mold getting to the plant. Don't mess with it, just meet its basic needs and the plant should take care of the rest.