As a coach: If seven minutes of running are a problem your endurance is a problem. I would recommend going for brisk walks every day to get better at cardio stuff. If not for your sport (it will improve your recovery and thus make it possible to train more without getting overtrained or even...
Interval work and just aerobic work in general. You could just go ride your bike to school/work every day. That covers at least the basics. Add some HIIT at home (no need for impact work, do Kettlebell work, squats, deadlifts etc. instead) and you are all set.
You need to see a doctor and get x-rays to rule out a fracture. Then find a physiotherapist to ensure optimal recovery. In general use lots of ice all day long, put the foot up all day long.
Fries (fried in fat!) and hamburgers let alone chicken nuggets (fried in fat!) not cooked by yourself are usually highly processed foods, so yes, this is "fast food" to my German mind. Here this is nothing we would feed kids (!) several (!) times a week. These are treats for special occasions...
Fast food several times a week? Wow. Perhaps a cultural thing. In Germany this is not the norm and considered a treat for kids, definitely nothing to eat several times a week even for non athletes.
Please be very careful with Crossfit. It has a huge injury potential and is not ideal from a GPP perspective. I would stick to your gymnastics conditioning or add some olympic weightlifting (not for endurance like in many CF-Wods, just for strength and speed). Make sure you get a coach who knows...
It will be fine. You can not "overtrain" working out two times a week several days apart. Keep going, suck it up. If the pain is really bad try to add in light (!) strength work on your off days and use everything that increases blood flow, like going for a bike ride, light jogging, walks, hot...
She should be doing lots of little games and activites with other kids her age to improve strength and speed, jumping and having fun. Think tag or running up and rolling down hills and the like. That is more than enough for age 7. Weights are not advisable for any 7 year old ever. Distance...
Negatives and hands on raised surface. For some folks this will be the wall. Work your way down over some weeks or months. Dropping to your knees changes the exercises too much in my opinion.
It is more difficult to relearn a already drilled in skill in a slightly different way than to learn it the right way from the start or (in this case) to learn the more basic skill first. Really, this is a standard problem in CF classes. Most people are able to handstand walk, nearly no one...
Walking on hands leads to people who can walk on their hands just fine but always keep running away on those hands instead of standing still and balancing. Ask a quadrillion crossfitters trying to hold a handstand without a wall. Walking for many meters but that's about it. Very hard to break as...