Why contacts are not display in address book but available when typing number?
You have 124 contacts saved to your phone. When you press +79, you get 449 in the dropdown. This 449 represents the number you have dialled (starting with +79) till date, from your device. Those may be the saved numbers or unsaved too. This is not a bug. Hope this satisfies you query. 

Update - adding the screenshots of my Lg 5.0.1.  When I search for contacts starting with 7 in Contacts tab, 250 contacts are shown.



While, when I type 7 in dialer, 396 contacts are found.


That's what happens with every phone. It's not a bug.