Seasoned Android users possessing highly moddable phones with immense developer support have often come across Paranoid Android, a custom firmware series that allows your phone to run in hybrid UI mode. This means your apps can be run in any UI style or DPI you want, irrespective of the device’s UI layout.

Paranoid has been based on AOKP and CyanogenMod in the past. However, in the recent times, the Paranoid team has decided to adopt pure AOSP (stock) Android, and has made their Paranoid Preferences app closed-source. This has prevented unofficial releases of the Paranoid ROM for certain devices.

Now your device does not have a Paranoid Android release? Or are you using a different ROM? Here’s a workaround.

Here comes the Xposed framework. It claims to modify the behaviour of apps without editing their apk.

Requirements

   Xposed installer by rovo89
   App settings by tungstwenty

Hit the links above to download the apk files.

Installation

Make sure your phone is rooted. Make a Nandroid backup via recovery. Install XposedInstaller apk. Run it and grant superuser permissions. Hit install/update and then reboot phone.

Install the Per App density setting apk. Launch the Xposed Framework App. Then in the modules tab, enable the Per App Density Module. Then reboot.

Launch the App settings app and then you can modify app densities for all the apps listed.

App settings you can try

1. Enabling Phone UI for apps on tablets or phones running a ROM with a non-standard DPI.

Select an app, set the DPI to 240 or 320. Set the resolution to 480×854, 600×1024 or 800×1280, and then hit the save button on the top right corner.

2. Enabling Phablet UI for apps

Select an app, set DPI to 213 and choose 800×1280 on the resolution dropdown box and then save. You may also choose between 213 to 178 DPI.

3. Enabling Tablet UI for apps.

Select an app, set DPI to 160 and choose 600×1024 or 800×1280 on the resolution dropdown box then save. You may also choose any value between 177 to 160 DPI

FriendCaster in Tablet UI

4. Run Play Store in Tablet UI

Launch the PerAppSetting app. Look for Play Store app then set DPI to 160 and choose 800×1280 on the dropdown box. Save. Look for com.google.android.gsf app then set DPI to 160 and choose 800×1280 on the dropdown box. Save.

Trivia

The App Settings app also allows you to modify the app permissions, hide/show the status bar and enable/disable persistent (sticky) notifications. Please be careful while handling such settings, as a misconfiguration can make an app malfunction.

Bonuses

The app settings is not the only feature out there. The Xposed framework allows you to apply a variety of other mods, the notable ones being:

   Play Store fix for ROMs with non-standard DPI
   Enable call recording
   Enable long length SMS sending
   Tweakbox: A big collection of tweaks for ICS (Android 4.0)

http://technofaq.org/posts/2013/04/how-to-change-apps-display-dpi-and-ui-without-paranoid-android/

I've got paranoid android since my galaxy mini and firefox never didn't show any tablet layout. Only 360p, and even setting the dpi lower than 120 it stays in phone ui. So, i thought there was a specific setting to change it. I'm extremely pleased my answer got a reply so quickly. You're awesome guys!

I'm on a nexus 4, PA 3.99RC