The Polsen HPC-A30-MK2 Closed-Back Studio Monitor Headphones included in the Shure Dual MOTIV MVL Lavalier Microphone and Two-Person Interview Kit can be used for mixing audio tracks. However, you may want to consider better quality headphones with an extended frequency response range for mixing a feature film.

Agreed, Jeff P's answer is correct.

This device requires a powered 1/8 jack to operate and is intended for use with mobile devices. This is a MEMS microphone, which is very similar to a condenser in its functionality, sensitivity to acoustic detail and requiring a power source to operate. The chief difference is, however, that it operates on less power, the kind already being provided by every mobile device with a compatible 3-ring 8th-inch connector. This way, the MVL is plug-and-play with no need to toggle on an additional power source in order to use the mic, and power drain on your device's battery will be minimal while the mic is in use.

The cable and mic measure about 50 inches total (1.3m)

This mic has a 4 pin 3.5mm plug that works with iPhone or iPod touch, and it needs phantom power. It might work on the gopro, but i think it would use a 2 or 3 pin mic.

I'm not sure, but it works great with the iPhone 6s. So I see no reason why it shouldn't work with an iPad, since there built with the same technology as the iPhones, but I've never tested it with my iPad. My talent uses it for VOs and radio ads that he does on a weekly bases and it works great.

Yes, it will. Please note, this setup would be meant for recording audio to a video or voice memo only.

Agreed, Mark S's answer is correct.