1. Last checked, no dashcams have IS feature.
2. You mean release from the mount? Actually depends on you
3. It's a dashcam. Not action cam. But yes can use the dashcam outside of the vehicle to record maybe for about 5-10 minutes as the lithium battery is only 240mAh. There is a power button for you to turn on and off the dashcam.
4. Yes.
5. I usually never take down my dashcams. No matter it's capacitor or lithium dashcams.
6. Not yet. Maybe in the future, Mijia will release an English firmware.
7. Did you go thru my review? There is a picture on my blog that I've translated for the menus on the Mijia dashcam including the Gsensor settings. I did mention more translated menus screenshots on my blog. Yes, you can off the Gsensor.
8. Nope. Only able to download the 1-minute video to your phone. Think most smartphones can do video cropping if not mistaken. I prefer taking down the microSD and use my computer more. But I do have an OTG microSD card reader in my car.
9. I'm sure on post #1, I've got put some Mijia Dashcam VS Yi Dashcam videos that I did. Anyway, I got some asking me to do new VS videos for Mijia dashcam vs Yi Dashcam King Edition (aka Ultra) vs SJ Dash. Maybe after my Vicovation Opia1 and ThinkWare F800 Pro review first.
10. Yi Dashcam is 2 years old specs. Unless you're talking about the new Yi Dashcam King Edition (aka Ultra). Then maybe that King Edition as the I saw some advantages over the Mijia Dashcam.
11. Well, usually no dashcam can capture license plate clearly at night while moving fast. Unless you have an accident, then cars usually will slow down and you can capture the license plates clearly.

Hope I answered all your questions