What free applications or programs that is good for making videos?

I'm a senior in High School, and i have to do a gym video assignment on picking one muscle group, it can be like calf, quadriceps, triceps, biceps and such…

But, the problem is that i don't know, which applications or programs is good or at least accomplish the job. Like, I want to add captions ((explaining the muscle group I chose), I want to put pictures, some effects on the videos and even some background music.
(Note- The video i have to do is just maximum of 1 minute noting longer than that)
(Note 2- You can list all the applications/programs whatever it is on computer or even for my phone that is an iPhone)

IMovie

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