Not all USB mice will work with an adapter. If it did not originally ship with an adapter, that you lost and are now replacing, then odds are it will not work. A USB hub adding more USB ports may be a better solution.
iPads do have usb ports. You just have to buy an adapter
No. Just the opposite.
Most modern laptops lack any sort of "legacy" ports such as serial ports, let alone them having two. Some older laptops did have multiple serial ports, but there's little point in recommending one because there's no guarantee you could find one. There are options for adding serial ports to a laptop, such as a USB to serial adapter, or a PC card with additional serial ports.
Its Parallel and Serial
Loop-Back
Loop-Back
The only parallel to USB adapter I've seen is one which allows you to hook up a parallel printer to a USB port on the computer. You could not use that manner to create USB ports.
RobertHoward and Prentice Robinson
You want a USB hub.
It depends on the adapter, but all USB devices will fit all USB ports, and all HDMI devices will fit all HDMI ports.
As many as you have free ports and power of the adapter. You have to espect a little (sometimes huge) drop in the communication speed between compmuter and USB devices connected through the wi-fi usb adapter.
Ethernet