Go to settings (should be on your front page if you didn't relocated it) - click on general - then passcode lock.
Yes you can but it's not as polished as the iPhone's lock or an Android phone's lock screen. And if you meant does this phone have a "lock screen" when you put it to sleep like the iPhone, no it doesn't
The screen of the iPhone 6 is 4.7 inches.
Screen lock - is an option to stop accidental use of he phone while (for example) it's in a pocket.
Nope. But you can take screen shots of them.
The symbol of a lock with an arrow around it on the iPhone 6 is called the "Orientation Lock" icon. It indicates that the screen orientation is locked in either portrait or landscape mode, preventing it from automatically rotating based on the device's position. You can enable or disable this feature through the Control Center.
To keep your iPhone screen in a vertical position, ensure that the screen rotation lock is enabled. You can do this by swiping down from the top-right corner of the screen to open the Control Center and tapping the rotation lock icon, which looks like a lock with an arrow around it. If the icon is highlighted, rotation lock is active, and your screen will remain in vertical mode regardless of how you hold the device.
I don't know and why is this listed in iPhone?
Yes I Use it every day it is my lock screen on my Mac and IPhone 4
When you are at the lock screen, follow the "slide to unlock" message by sliding the screen to the right. Then input your passcode.
double tap the home button while the iphone is locked
4.7 inches.
4.7 inches.