Because every search engines will give you a different result. By searching with multiple search engine you can get more result and cover a bigger area.
Different search engine has different algorithm about how they programmed to do the search. They also have a different database that will be searched for. That is why the same keyword will not giving the same result.
In order for me to answer this I need a photo of what the "invisible marks" are
What do you mean? Pop up settings only block or allow pop ups. They should be pretty similar if not the same.
The most likely problem will be the drivers of the scanner it's either too old or windows 8.1 don't have the old scanners drivers
so all u have to do is get the scanners drivers