I got a Lenovo K3 Note with Android Lollipop 5.1, my problem with this phone is the hugely modified Android system. For example, there's no Settings > Applications or Settings > More menu in the Settings app.
How to restore the default Android settings manager so I can unlock these settings features?
To expand on Andrew's comment, Settings is a core system app that is tightly integrated into the ROM. There is no way to replace it without flashing a custom ROM, and modifications like enabling or adding features would require building the Android source for your device.
If you are rooted or can use ADB, etc., there are a number of other ways to manage applications and settings — for example, uninstalling apps. Feel free to search the site and ask another question if you want to do something specific that hasn't already been covered.
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