This is so easy to install any handyman or a friend with drill and a correct size hole saw, can install in about 10 to 15 minutes. Great viewer at a very good price, I purchased 2 of these, one for front door and one for garage door. I hope this helps. P.S. Home Depot also sales hole saw kits to install this door viewer.
That's true, you can not see inside house with this viewer.
The required hole size is 1 1/8", you would need to add a shim to take up the slack.
Not very well. It’s like a magnifying glass, you can’t see much and what you might see will be distorted. If seeing something from the outside in them put a small cover over inside peep hole. Remove it when you want to see who’s at the front door.
I also have a screen door on the outside of my door, and I can see perfectly fine.