(Feel free to skip to the "The Problem" section. This section is included for completeness, and just in case if it actually is related.)
SMARTPHONE: SONY Xperia E C1504
-RAM: 512 MB
-DATA/SYSTEM space: < 1GB (~700MB)
-DATA/SYSTEM used out-of-the-box: ~ 300-400 MB
-INTERNAL STORAGE: ~ 2 GB
-PROCESSOR: Qualcomm Snapdragon S1
-STOCK ROM: SONY: Android 4.1.1 - based ROM
SD Card: SONY 32 GB microSDHC Class 10 (U1)
The stock SONY ROM that comes with the phone is too bloated, filled with unnecessary features, apps, and other stuff that make the phone (close to) unusable. Not only that, but even more space is wasted with some "SONY PC Companion" installer that I don't really need (download it from internet, maybe? and NOT WASTE VALUABLE SPACE!!!)
It's so crazy, that I can't even update all the apps in the phone (even without installing other apps in Google Play) without getting "Can't update : Insufficient space available.". Not only that, but 512 MB of RAM struggles to keep up with Facebook/Twitter! (Yes, they come pre-installed.). Way to go, SONY.
(barely) Survived for 2 years, after rooting using KingoRoot, removing loads of system apps, getting an SD Card, and installing Link2SD. After that, some apps just stopped. Knowing an update was pending, decided to Unroot -> Use PC Companion to do clean install. Still SLOW, and storage problem persisted, so decided to Unlock Boot Loader -> Install TWRP -> Install CM10, CM11, or CM12, whatever was available. Latest that worked was CM11, but without camera (bummer), so CM10 was used. So much for Lollipop. :(
Running CM10 smoothly, updated everything, and installed a couple of apps, and now only 150 MB available. :(.
Installed Link2SD, created mount scripts, and rebooted. Now some apps that were previously on SD card, including Play Store, Play Services, Nova Launcher, etc. appeared magically. Since some were installed in CM10 after wiping, the were replaced by their respective SD card versions.When opening any of those apps, I am greeted by "Unfortunately, has stopped.". Recreate mount scripts / relink apps / etc, and prompted for a reboot.
Except the reboot eliminated all trace of those apps. Means Google Play Services is GONE!
Next logical step: delete those files and start over. Used an adapter, and it mounted it read-only!!! Tried other adapter: (seems) perfect. After deleting, unmounted SD Card. Surprise! Everything is back again!
Tried GParted (deleting all partitions and creating new ones, as well as destroying old partition table), and to no avail. Everything is back!
shred -f -v -z -x /dev/mmcblk0, and no errors reported.
So I'm left with yet another SONY product that doesn't work as it should. And it's a shame as I used to trust SONY products, as I thought they were of good quality.
Non-working or impossible:
-Buy a new phone.
-Deal with it, and just use the phone for calls and SMS. No WhatsApp, Telegram / Plus Messenger, etc.