A:AnswerThe usb-c is not connected to the graphics card so you will not be able to use an adapter to get it to work. You either have to use the VGA (possibly with a VGA to HDMI adapter) or update the graphics card.
A:AnswerIt means the item is “out of the box”. This is usually, but not always, a store item (computer, tv, etc) that was on display in the store for customers to view. It’s discounted because it’s not brand new sealed in the box, but the box was opened, and the main item displayed. It should be in good working order though.
A:AnswerHere is a link to the motherboard specs: https://support.hp.com/us-en/document/c06432435
Here is a link to the main specs: https://support.hp.com/us-en/document/c06441496
A:AnswerUnfortunately, it does not have a Mini-ATX motherboard. The motherboard used in this computer is slightly wider and shorter. I don't know if the mounting points would match up.