To delete a file or folder without moving it to the Trash, open Terminal in Applications>Utilities and copy/paste
sudo rm -rf
Then, important, leave a space after the -rf and drag the file or folder into the Terminal window -- it will then appear with the path of that file or folder -- and hit return. You will be asked for your admin password -- nothing will appear as you type it in -- and given a warning about using the sudo command, if this is the first time using sudo.
Note: the rm command, especially run with sudo (sudo gives you root access) is a very dangerous command; it must be used with great care. No second chances.
You cannot selectively empty the Trash. It's all or nothing. If you want to Trash a single file or folder, then move all the other ones you don't want to empty out of the Trash.
AFAIK, dragging a file from one volume or drive to another should leave the original in place and move a copy over. I've never heard of any exceptions. However, if you are dragging a file or folder over using the Finder, I don't think the Permissions for the copy will necessarily be preserved, except for files or folders moved within your user, where your user is already the owner. Even within your user, the owner may be changed to your user, even if you are not the owner.
Outside of your user, the permissions will be changed to reflect your user as owner, which will be wrong. So it's not a great way to copy over anything from /Library or /System/Library using the Finder, where the owner should be system or root, or other, not your user. If you do this, it's probably then a good idea to repair Permissions, so they are restored properly. That said, Permissions repair will not touch anything in your user.
Moving things with the Finder isn't always the best way to do this.