if u have a page lets say with the name "ABC" and you create another page by selecting the "New Page" option but with the same name i.e ABC, then the new page will over write and replace the previous page without any warning.

is this normal. it should either warn or created a duplicate.

Should warn, but apparently does not. A bug that needs to be fixed.

preferably it should change the filename by adding (1) at the end and keep both pages