LG P760, insufficient disk space, help please I have an LG P760 updated to the latest available by LG version. 
The last couple of days I cannot update the installed apps with the known error of insufficient disk space, although it was supposed that more than 290MB where available. I removed some apps and increased the free space to 320MB. Then I managed to update some apps but that's it.

Now, I understand that this is complicated but I want to know the following:
a. Is is possible to partition my external SD and use it as internal storage?
b. I want to avoid to root the device. If it's not possible, is it possible to root the device and then un-root it? 
c. I want to avoid apps like link2sd. I am fairly competent with Linux CLI, so, I would like to use the mount command and Android boot scripts in order to mount SD partition.

Can I do that?



New Info:

It is possible that I found a "bug"(?). I had 2 devices and both of them were under my account in the Play store. I gave the second one to my wife. For a reason that I don't understand, my device was "removed" from my devices list, but the device that I gave to my wife was not (and it was in my wife's account too!). 
I wanted to install an application and since I could not do that from my phone, I decided to try to "push" the application. But Play store said that my device was not compatible (and it showed the device of my wife). Then, I hide it, hoping that my device will re-appear. 
Instead of that, my upgraded the apps that until some minutes ago refused to do so with the "insufficient" storage message!
a) Yes, you can use your external as an internal storage. (Requires Root access. Using link2sd. I don't know any other app) 

b) Yes, it is possible to unroot your device. (http://www.wikihow.com/Unroot-Android)

C) I haven't tried that. But, yes you can do it.

I think that you want to avoid using link2sd app because of the risk.So I suggest you move your apps from Internal memory to an External memory(if you have any).
By rooting your phone your warranty will be void, plus you take a huge risk.(But if anything goes wrong, you are not alone. So you'll always find a solution on net :p )
This is the biggest disadvantage. But on the bright side there are plenty of things you can enjoy.