Moto E / Lollipop 5.1 folders not mounting via USB

I have 4 files on my computer (Ubuntu 14.04LTS - Trusty Tahr). I have a Moto E (Android Lollipop 5.1 stock rom). I do not have "Root" access. I want to sideload, via a USB cable between the two devices to transfer (copy) the files from the 'puter to the phone's SD card memory.

On plugging the phone into the computer, an error message appears saying "cannot mount" and then in another window, asks "what do you want to do?" I select Open Folder. But I cannot copy files to the phone. Exception 6 is the code.

What is going on here and is there a way around this problem?

Synchronize two folders on Android with all subfolders + files in them? Not PC-Cloud!

The question is about synchronizing two folders residing on Android phone itself.
I've spent hours experimenting with no success.

I found programs syncing two single folders but not syncing all sub folders and contents inside subfolders multiple layers deep.
Programs offer cloud and PC synchronization but what about simply two folders both inside the Android phone, with no internet or any other connection necessary?

The obvious goal being synchronizing removable SD Card folder content with internal SD card folder content.
I've tried Google Playstore search and I have a headache from hours of not being able to do a simple two folder sync using programs that claim they are sync programs - but they can't sync two folders with subfolders inside them. I don't want to sync with PC. I don't want to sync with the Cloud. Just simple two folder sync in Android.

Synchronize two folders on Android with all subfolders + files in them? Not PC-Cloud!

The question is about synchronizing two folders residing on Android phone itself.
I've spent hours experimenting with no success.

I found programs syncing two single folders but not syncing all sub folders and contents inside subfolders multiple layers deep.
Programs offer cloud and PC synchronization but what about simply two folders both inside the Android phone, with no internet or any other connection necessary?

The obvious goal being synchronizing removable SD Card folder content with internal SD card folder content.
I've tried Google Playstore search and I have a headache from hours of not being able to do a simple two folder sync using programs that claim they are sync programs - but they can't sync two folders with subfolders inside them. I don't want to sync with PC. I don't want to sync with the Cloud. Just simple two folder sync in Android.

How to get access to System folders when making a new app?

Does anyone know how to get access to system folders when making a new app? I am trying to create a new Ad Blocking application for windows (Based on AdAway from android) but cannot get permissions to write to C:\Windows\System32\DRIVERS\ETC\HOSTS.

Can anyone help me out super quick?

File manager with smart folders ( filter )

I backup my photo from SD to external HDD, I connect my HDD to tablet with OTG cable
in photo folders i have RAW + JPG and it king to get difficult to view only JPG
any file manager allow to create a smart folder that filters single folder ( and subfolder ) contents?
I'm on samsung tab S but samsung file browser doesn't seem to allow this
I also tried FX file manager that is pretty cool, with spit view, but i can't find a way to do that

I guess is not possible with IFTTT to copy all JPG to a new folder

Where did my folders and files go?

All the files and folders on my Galaxy Note 3's internal and external storage have reverted to what appears to be the defaults, all the photos (DCIM folder), videos, downloaded files, apk's, setup files, language files and who knows what else are gone, just vanished, not visible in Windows nor in Solid File Explorer, some apps are missing their language files or data files.

The phone was plugged in to USB on a WIN7 PC and the explorer window seemed to freeze, eventually I had to unplug the phone and now when I reconnect or look with a file explorer there must be >40 folders and thousands of files missing.

So what happened? Where are all the files? Are they recoverable?

Folders: Is there any way to have more than 9 icons without scrolling?

There's certainly enough screen real estate for at least one more row. And if they weren't spaced 25 miles apart there would be plenty of room for another column as well...