Can I turn a PC into a RASPBERRY PI for making RASPBERRY PI projects and use the usb's as the gpio pins

If you mean input/ output. I think you can.

But you have to use a "PIC" or a "PID" https://en.m.wikipedia.org/wiki/Programmable_logic_device

It's a bit of a waste of a full desktop PC or server. The Raspberry Pi is a low cost, credit-card sized computer that plugs into a computer monitor or TV, and uses a standard keyboard and mouse. It is a capable little device that enables people of all ages to explore computing, and to learn how to program in languages like Scratch and Python. It’s capable of doing everything you’d expect a desktop computer to do, from browsing the internet and playing high-definition video, to making spreadsheets, word-processing, and playing games

I don't think so unless there are emulators.

https://youtu.be/EE--H1wYKGU

U can use VNC Viewer on your pc to use your rpi. There are tutorials online. You basically enable ssh, then VNC server over a terminal like putty. Then simply use ur pc to use/programe with the raspberry