How many iCloud account can created in one iOS device?

You will lose everything saved on the iPhone, so make an iCloud or iTunes backup first. As I see that you can't log in iCloud, connect your iPhone to the computer and iTunes will create a backup. Then, go to Settings > General > Reset > Erase All Content and Settings to erase your device

3 iCloud accounts is the limit for one iPhone, iPad or iPod touch. If you want to carry on creating iCloud accounts, you have to restore the iPhone

You will only lose the content stored on the iPhone, not your iCloud accounts. You will be able to access to them from other devices and on http://www.icloud.com

It won't affect to the 3 iCloud accounts created on the device