I wanna update my phone into iOS 14.2 will my data be removed or not . I have 256 gb iphone .

In 10 years of doing iPhone updates, I have never had an update remove any data. That includes iOS 14.2. But Apple does suggest that you backup your iPhone before updating. See: Update your iPhone, iPad, or iPod touch - Apple Support

Basically what FoxFifth said, the chances of your data being lost are little to none, but it helps to be extra safe and make a backup, just in case.

Besides, mrakbinumer, with a full backup, you have the potential to “back out” of the update, if something causes trouble, for you.