Yes. You can use the camera (indoors, outdoors and underwater) completely from the buttons and touch screen interface. No phone or remote control is required. Those other devices just add flexibility.
There are options for saving the video. If you have the app, you can transfer the images via wifi or USB. You should also be able to use an adapter to connect the card to your Mobile device, MacBook or PC and pull the files off the card that way…via a photos app or the file manager.
I’m not certain, but I suspect you can make a video that long. Batty life is the question. I’ve never checked to see how long the batty lasts. It will depend on image quality, I’m certain. GoPro does allow the camera to be powered externally via USB-C, so if the internal battery doesn’t have enough capacity (which it may), you can power the camera from an external source.