Want to downgrade Android?

 In this segment of Ask AC, we tackle what you need to know before you decide to downgrade Android on your phone
Make sure you want to downgrade your Android
The easy stuff first

• Back up everything you can to the cloud

• Download the factory image of the version you want to run

• Flash it

The hard stuff
Custom ROMs
Most of us here are update junkies. When a new version of Android (or anything, for that matter) is announced, we start bouncing off the walls and worrying about when we get a chance to have it and enjoy the changes. When it's a new version of our operating system, things get even more frantic. We look for leaks, we try custom ROMs based on the new stuff, and we're ready to sideload the minute the right files appear. It's half the fun of owning an Android, and we just love the fluid state of software and the constant changes.
But not everyone feels this way.
Some of us need to stay on an old version — or think we need to stay on an old version. Maybe you've read about some bugs that you don't want to encounter. Or maybe the new version breaks support for something you want or need. Or battery life issues and reports have you skittish. There are any number of reasons to want to go back, but it's not as simple as it sounds in most cases.
Let's discuss both the reasons for needing to downgrade your Android, as well as the feasibility of doing the deed.

Moving backward and installing an old version of Android is not without its own set of headaches. First you'll have to figure out how to downgrade, which we'll talk more about later. After that, you may find that some of the things you really like just won't work with an older version.
Google introduces new APIs for developers with every iteration of Android, and folks like Samsung or HTC add their own on top when they customize Android. Many times, these are not backward-compatible. Some of the changes you won't get to use may be minor and seemingly unimportant, but there's always a chance that something you really need or love isn't going to work with an older version. There's no real way to fix this, and if you find yourself bouncing back and forth because of features, look into a custom ROM or two. Our Android forums are your friend here.

Nexus devices, or any device that has a standard factory image and unlockable bootloader, are the outliers. If you want to go back a step or two with the OS the method is simple.
There is a lot of stuff you're not going to be able to back up without having root access. Know that things like game progress, message histories, photos and videos — as well as the data for all your applications — may be gone forever, because a downgrade of the OS always requires a full device wipe. Check into the various backup and restore apps, get your photos and videos into Google+ or other online storage, and be sure to talk to your friends and fellow users in the forums before you click any buttons. Likewise for the right way to flash an image, which usually requires parts of the Android SDK and a few commands at the terminal. Let the folks who do this sort of thing for fun be your guide.
For those who want to roll back to an earlier version of an app, the good news is that this is really easy. You need to be prepared though, because you'll need to find an old version of the apk file. The good news is that those are really easy to get. Install one of the many file browsers that can backup apk files. They will place an installable version of the app right on your device storage, which you can install anytime you like. You'll need to uninstall the newer version, which deletes all the app data, so know going in that you are starting fresh. If you're the type who isn't afraid to go back to what's more comfortable, build your apk library (and keep it updated with the versions you like) so you're prepared. I use Clean File Manager to back up my apk files, if you're looking for a recommendation.

The thing is, most folks us aren't using a unlockable device with factory images all packed up and ready to flash. Companies like Samsung or LG and the rest usually don't like to share an installable version of the OS, and tracking down something you can flash for your Android may prove very difficult.
Oftentimes, finding it actually is the easy part. There are other hurdles to overcome. Normally, an OS update also updates the device's bootloader. It's not uncommon for a specific version of an OS to require a specific version of a bootloader, and bootloaders are not one of those things you can just jump in and change on a whim. You're going to have to do some serious research, and then procure the files, and then sort out the method to flash them. More often than not — again, we're not talking "Nexus-like" devices here — this involves some serious warranty-voiding hackery. And be warned, doing things like erasing or overwriting a bootloader or radio file is one of the few ways to truly brick your phone.
I'm not trying to talk you out of it, but I do want you to know that the 5 minutes it takes to flash your phone back to an older version has hours and hours of reading as a prerequisite.

If you're serious, and don't mind losing your warranty, a custom ROM is usually a better choice than actually downgrading. You'll have the newest version, and there is a small army of volunteers working to fix the bugs and annoyances. As an example, many custom KitKat ROMs for the Note 3 look and act just like the factory version, but have all those AT&T or Verizon apps pulled out, and Jelly Bean-style support for the SD card baked in. The only way you would know you're running a custom ROM is that it's visually faster, and your file manager can copy files all over the SD card. Custom ROMs are an option everyone looking to downgrade needs to consider. The best place to find out information about what is available for your particular device is the forums. Ask the Android geeks who love to tinker — and use the same phone as you — where to begin.

Source:- androidcentral