They were made by Sauron’s boss. They breed on their own. Sauron has to convince the orcs to work for him; this was tough when he was in his more angelic form.
You might be thinking of the "genetically enhanced" Uruk Hai orcs created by Saruman.
Quite possibly. I was never that deep into it, but have many many friends that are so I had heard them discussing various aspects. Clearly got some wires crossed
If I'm not mistaken, Melkor (Morgoth) created orcs by corrupting elves. Saruman created Uruk-Hai by breeding orcs with humans.