I have a Windows 8 laptop which I updated to Windows 10 a few months ago. My laptop has been pretty slow since the update. I uninstalled a few things (from where I already installed on Windows 8). If I reset my laptop now will I have Windows 8 on it again?
That depends on how major it resets. Windows 10 offers to restore its original state. But if dzú takes a boot partition of the laptop with Windows 8 on it, Windows 8 will recover.
Better find out what slows down the laptop. Perhaps you are just missing the correct graphics driver (search on the manufacturer's website) or the hard drive is full. Does the computer have at least 4GB RAM? Which programs are running in the background?