Do you consider OK to take the 30 day challenge from 7 min workout app and then do something else like running? When is the perfect time to change an activity?

The perfect time to change activity is every day. Even Scientists prefer that it's better if you add different activities in your active life. If you do bodybuilding or just fitness it's almost must to do yoga for better flexibility.

I would just get a different app that had to do with running or make a step challenge for your self like take 10,000 steps a day & you can check this in your health app

You bet , the more you change it up the more fun it will be and you won't get bored. Challenge yourself and then, enjoy what gives you the most satisfaction. I am a walker, but I like to see new places and different locations that have multi levels of hardship.

I think it’s ok when you have the time to do so. I only stick with 7 mins when I’m pressed for time otherwise I try to at least do a 30 minute workout. The best time I find to make a change is when my body feels like it has plateaued in a workout and there’s no more room to push; a one minute squat starts to feel easy so I add more weight.

Yes, change whenever as long as you keep it consistent, do some form of excercise each day. Find out what you most enjoy

Absolutely! The point is more to 7 minutes of ANY exercise as oppose to being one specific routine. Whatever exercise you actually feel like doing that day, go for it. It's better in long term to enforce a habit to be flexible and do to something that feels good in the same vein as the habit instead forcing yourself to do a rigid action that you may not feel like that day.

The point of the challenge is to develop healthy habits. If you’re working out for 7minutes, it doesn’t matter what you’re doing as long as you’re continuing your healthy habit. Change the activity when you need to because if you don’t change it up then you’ll lose interest and it won’t be fun and you’ll lose the habit. Don’t forget to celebrate with a happy dance or wiggle!