Yes, our underwater camera for snorkeling supports instant playback of videos directly on the device, and you can also upload videos to a PC for viewing. 

Hello, please check if the rear camera is fully inserted into the dash cam main body. 

It HAS an Auto Focus button. Works great! As for the Anti-vibration/shake, NO, not that I can see. However, a hand stabilizer handle should help with that. I haven't notice any vibrations although I'm still experimenting. Beautiful video! FYI,Can't find an external monitor that works with this camera. Purchased two different monitors and five different HDMI Cables, No luck. But the flip out built-in is fine. Good quality, I just wanted something larger. 

Yes, please watch this video https://youtu.be/UU4sKfzW_uQ. 

With this filter, I can reduce my shutter speed, even with a sunny day, so in my photos I get a blur motion background. Same thing with video, you can reduce the shutter speed so you will get more motion blur. It you consider for portrait, this filter don’t add blur background. For that you need a 2.8 or faster lens. I hope this help