Help! My Inca i3642B Tripod's baseplate is screwed on too tight to dislodge onto my Nikon D5600 any help would be appreciated. Thanks. ?

As well as qrk's suggestions you could try a couple of drops of something like WD40.  Spray some into an empty jar / tin or whatever and apply it with a small brush.  Keep it well away from the lens!

The screw's head in the photo doesn't appear to be damaged, or at least not so damaged that you couldn't use a screwdriver.  Use an appropriately-sized screwdriver and that should do the trick.  By "appropriately-sized" I mean one that has a length and thickness as close as possible to the actual size of the slot in the screw head.  Using a screwdriver that is too thin and too short will be problematic.

That sort of fastener is probably meant to be used with a coin to tighten/un-tighten. Or, you need a really big screwdriver blade which is not commonly found in most tool boxes.

If the bottom of the fastener slot is flat, file down a penny so it is flat. Use vice-grips or pliers to grip the penny and unscrew the fastener.

If that doesn't work, try turn the baseplate with pliers. Wrap 5 turns of masking tape around the baseplate edge to prevent the pliers from marring the baseplate edge. Be careful doing this as you don't want to damage your camera by forcing the rotation.