[Huawei Ascend P7] drguild:
Apologies if I came across about abit hard this forum has had allot of impatient people jumping in recently trying to run Emui 3 on l10's then asking to downgrade as you may have noticed the other teams like paranoid are already dealing with lots of people saying there to slow for not having lollipop out within a hour of aosp.

I had the same issue running a custom Minecraft server that people got really angry then refused to play and bad mouth the server if we didn't update that day when update time for us was about a week given the number of customizations we had 41 plugin's in the end, sometimes longer if there were more changes the mod and custom server devs had to deal with.

Emui 3 and lollipop has more bugs more as it's new from what I found I may start a proper consolidated emui talk thread later for those running it opposed to all the l10 when are we getting it out help me downgrade threads.

The place I think you should start is to download the source code for your version from the emui webpage and start analyzing it out of interest.

There's another Dev on here doing the same thing so you might want to contact him for info.

Also there are tools on Linux that easily let you unpack stock image files and the ext container and repack them.

That way you can see the full file structure and how a rom is packaged.

It's good just to see what's inside roms and how the first roms are usually made by a repackage before source.

I will stress the same as above that while these are starting points you would need to know what you are doing and something more hackable like a cheap nexus or or Chinese tab (about $50 USD) with easy upgradable firmware something would be better to start on.

Also grab down the android tools with eclypse for Linux, the sdk virtual device and have a play around making a app and stuff also you can edit the virtual rom safely etc.

The Linux version of the tools is far superior as you can natively mount the virtual ext cards for host file transfer and do other things which you can't under windows.

By ext above I mean the virtual partition files which are either ext 3 or 4 last time I looked.

I'm not a coder myself and I only did basic stuff in the past as I had a Chinese android 2.2 tablet the MID ones as my first device, I used a custom rom on which was just a repack with file system changes with bloat removed etc.

I looked into this out of interest and curiosity, each rom update I repacked it with the apps I used so I didn't need to reinstall them, there was probably a better (proper) way than just unpacking the ext file system from the img adding my apps in to the deploy folder and repacking.

Also I unpacked a APK weather app etc to make changes and use a custom background and others like themes to grab icons and assets this is a good start with looking at app packages and how that all works as well as making your own app in various tools eclipse for one which is the official tool but there's hundreds of android programming softwares online even to do simple stuff as make a stand alone html5 app from a webpage.

The tools on Windows I found were lacking and harder to find for the rom stuff, with Linux it was built into the system a lot of things.

What Linux is the best for doing Android stuff I don't know so that will need to be researched.

As mentioned devices can be dangerous for custom stuff especially newer ones with bootloader security, the older Chinese style ones and some others you could reflash easily from sdcard with a update.img file as they didn't contain that lock out security on boot and debugging.

I nearly bricked a few devices in the past, once having to rely on the bootloader and Android Commander a powerful tool and device terminal to mount the partition rw while in the bootloader to rename a file backI renamed as a test that caused the system to stop booting.

You can still get some tabs that do that about 50 USD on eBay etc I think.