As far as placing your phone in landscape mode, my latest response was to another poster, asher271. Now, your latest post gives me more information to work with. You cannot get back to the home screen from Standby Mode because the home screen on the phone cannot be displayed in landscape mode. You have to put the device back into portrait mode to view the lock screen, then you can unlock the device to the home screen. Sorry I did not completely understand what your issue was with my initial responses.
You can provide feedback to Apple that you would like to see that ability on the iPhone. Use this link. Feedback - iPhone - Apple