If the PC doesn't have WIFI buil-in, then you'll need this adapter PLUS a WiFi router AND modem. Most modern PCs have WiFi already. If you don't have a WiFi router in the house, just a modem, you'll need to also purchase a Netgear Wifi router. They're not expensive and they are easy to hook up. I used that combination for 6 years with no problems until I had to upgrade to a WiFi router/modem combination when I went with with Verizon.

I use it on a 6.5 year-old desktop. Highly secured? How do other PCs in the area connect? I use plain vanilla Windows10 Pro with a late-model Verizon WiFi router. If your system has other software loaded on the local PCs, you'll need it too.

Not by itself. If you have a cellphone that has a WiFi hotspot option (like the Samsung Galaxy and many others) the connection would be made from the Netgear WiFI adapter to the cellphone, then the cellphone would connect to your carrier's network (Verizon, ATT, etc.) using up your data rates. It would be slower than what you're probably used to but it would work.

I don't know for certain but I suspect not. It needs driver software and I don't know of a way to load it on a printer.