DON'T do that. It's going to cause you all sorts of headaches in the future. Since the path to the images are embedded in the map, it means that the map file won't work for anyone else not having the images copied to the right place, including on your own other/new computers. Leave official artwork in the folders they were installed in, and import them from there. Only make your own copies if you are going to actually modify the .png files on disk themselves, in which case you obviously need a personal copy.

You can also get a list of all the images in the drawing by using the LISTIMAGENAMESDWG command.

1 - Yes. But you need to import the relevant fill styles into the map. See this faq entry

2 - No. The software doesn't have that feature.

3 - I don't really understand. The icons you show in the image are already in one row. But generally, you can do whatever you want with them by editing the menu files

Note that if you bough a level that don't include CC3+, you won't have a program at all, but you can use the artwork installed by the collection in other programs.

Tools menu -> Options -> Pick cursor aparture