Will GPS spoofing + VPN on mobile hide location?
Suppose I turn on "developer" mode on my Android mobile phone and install a professional GPS spoofing app and a professional VPN app. Developer mode will allow the GPS spoofing app to overwrite my GPS location on the phone, whilst the VPN will redirect all data via a secure server.
Will this "GPS spoofing + VPN" combo prevent third-party apps from being able to see my location?
Would professional organizations, such as police or other government entities, still be able to locate my phone?
Google Maps uses your wifi for location services. So, no, it will not always work.
In fact, to answer your question, you should read how Android Location Services work to know what factors are used and what you would need to override.
Police do not need to use the phone's location services. The mobile provider can use their towers to locate you via the cellular signal.