I just wanted to make a slightly more updated and easier guide, as a follow up to this extremely helpful guide written here by tooplanx, and sourcing many of the same sources, but also some crucial new ones. I particularly spent hours looking up how to install the latest software (recovery and ROM), when in the end the solution was simple but not widely known and very noob-friendly. Here goes...
1) 1. First I downloaded drivers for the y300 from here: https://files.dc-unl...BE98BC29A9C1216
Extract the drivers and launch 'DriverSetup.exe'
Wait for this to install fully.
2) Next, go into your phone settings and turn off 'fast boot'. Turn off your phone and remove the battery for 5 seconds. Replace battery, and press vol + and - repeatedly and the power button for several seconds, until screen goes a violet colour.
Now connect your phone to your computer via USB and wait for the drivers to install fully.
3) Once your phone is connected, load up dc-unlocker. In the 'Select Manufacturer' box change it to 'Huawei phones'. Leave everything else as it is (including the 'select model' box).
Click on the large magnifying glass button. This will scan the phone for its bootloader code and show the unlock code required after around 10 seconds.
Copy and paste the 16 digit "Bootloader code" somewhere safe (like a notepad file).
Close the dc-unlocker, turn off your phone (you may need to remove the battery), and unplug from the computer. Reboot your phone.
WARNING- THE NEXT STEPS WILL FACTORY RESET YOUR PHONE: IF YOU NEED TO BACK UP ANYTHING, DO SO NOW!
ALSO: New(er - explain in a bit) files for the following located here: https://www.dropbox....O-ROOT-v1.5.zip
4) I then followed Step 2-4 from this webpage: http://huawei-y300.t...ascend-y300-all
At step 2.11 of the website instructions, when running 'unlock_bootloader.bat', type in the 16 digit unlock code generated by dc-unlocker. Follow the remaining steps to the very end... the SuperUser part is very important, and flashing the recovery is need to do this).
5) You should now have a fully rooted phone, with a recovery option to go. Now, if you want the latest and best, it may be advised to get a very recent ROM. However, to upgrade past Android 4.2 you're going to need the latest TWRP recovery to flash it - and doing this is easy. Just download the image file here (or search your device for later versions on the site), stick it on your SD card/phone memory. and head to the Play market. Search and download for Flashify - install it and launch.
6) Grant Flashify SU access when the prompt comes up. Select "Recovery Image" and locate the image you downloaded and moved to your storage earlier. Flash it.
7) Download your ROM. There's a whole list of suitable ROMs for the Y300 here; find the thread that suits you and go to it. Read what it says, any particular notes and what others say on the release.
I chose CyanogenMod 10.2 by Dazzozo since I thought 11 probably still isn't stable enough, and if you go to the download link on that thread you'll notice he's been continually updating his release since he launched that thread. My thoughts on it all later... but important to note, I used TWRP to flash it, not ClockworkMod like this thread suggests should be used.
---- AT THIS POINT: ------ Be cautious about following my steps. What worked for me may not work straight for your ROM, though I don't see why it shouldn't... someone else fill me in here?
8) Stick the ROM on your SD card. Also you'll need to download something called GAPPS (specific to the ROM you chose) if you choose a CyanogenMod ROM... this is because by default, Google apps are not included due to legality reasons. Click the link and locate the package applicable to your chosen ROM, then put that on your storage.
9) Boot into TWRP. Take your battery out for 5 secs, put it back in, power on and hold up volume until recovery boots.
10) Go to Wipe > Swipe to Factory Reset; Advanced Wipe > Check: Dalvik cache; Cache > Swipe to wipe
11) Go back to home. Do a backup and select all options > Swipe to backup.
12) Home > Install > (Select Rom) > Add more zips > (Select GAPPS file) > Swipe to confirm flash and wait till it's all done.
13) Reboot, hope it worked and just let it all load up. Hopefully you should be taken through set up and boom... you're done
Any problems, come here and I'm sure we'll be willing to help! Also, before going into complete panic like I almost did (didn't wipe stuff first time), breathe deep, take your battery out for 5+ seconds. Put it back in. Try boot into recovery again... as long as that works you are pretty darn safe.
My experience with Y300 and CM10.2:
Interesting. Considering this has gone through so many updates now it still feels very buggy; I get it is a nightly but it just feels slower on the resources - and this is exactly why I didn't want CM11 just yet. I think it is great you guys support our developers but I feel the phone is more sluggish than before I wiped it and programs close randomly at times. I think I would not have minded just having a new launcher like Apex put over the one Huawei provides and the default used Trebuchet launcher by CM didn't sit with me - but that is largely because it lacks a simple pinch to zoom function for the homepages which I find very important to me.
If anyone else can weigh in on how I feel, add alternative suggestions (ROMs; launchers; ways to improve system resources) I would greatly appreciate it.
Hope this helps someone; thanks to tooplanx for making the effort extremely easier on my part, and all the original posters before him/her. At the end of the day, we're all littler people, standing on the shoulders of the giants before us.