[Xperia Play Q&A, Help & Troubleshooting] skyx26:
Ok... it's more or less like this:

First you need to know if your phone can unlock bootloader. To do this, you need to enter *#*#7378423#*#* in phone pad/caller. There is no need for send.

You will enter a menu, there you must use touch screen to select "Service Info" and then "Configuration". In "Rooting Status" you should see something like

Rooting Status:

Bootloader unlock Status: Yes

If it says "Yes" then you can unlock bootloader.

A thing to considerate when unlocking bootlocker is: if you unlock bootloader using EMEI service in Sony Webpage, you will loose your DRM and warranty. If you don't want to loose them, you must use test point to unlock bootloader, but understand something, once you unlock bootloader by test point there is NO way to relock it again. If you unlock it by EMAI service you can always relock it flashing a locked bootloader... wich by the way, has no sense at all, why will you lock a bootloader once you unlock it???

Once you unlock the bootloader you could do almost anything with your phone, you could flash custom kernels, flash radio bands, install custom roms, gain root access, etc.

Now, do you need a unlocked bootloader?, that will depends on wich custom rom you want to install. There some roms that doesn't need a unlocked bootloader to install them.

After you have unlocked bootloader you must gain root access with SuperOneClick. Download it, unzip it, put your PLAY in usb debug mode, conect phone, run app, click Root. It's that simple.

With root access now you must install CWM Recovery. There are 2 ways to do it. First way is installing "CWM_Installer-v5.apk" (attached below). You must send it by Bluetooth and install it. When you run it, it will download and install CWM Recovery. Using this way will allow you to enter recovery by pressing vol down key when "Sony Ericsson" title shows after reboot.

The second way to install it is flashing a custom kernel. This is by far the easiest way. I recommend "Advanced Stock (with Recovery)", you can always choose another later on. Right now you only need access to recovery. To enter recovey mode, you must press your back button a couple of times when "Sony Ericsson" title shows after reboot.

Once you have CWM Recovery, you MUST do a full backup. No matter what you do later with your PLAY, if you (for any reason) want to go back stock, with a full backup you can always go back.

Now you are ready to install a custom rom. Wich one install?, that's up to you and what are you gonna do with your PLAY or what do you need from a custom rom.

Xperia PLAY has one BIG problem with custom roms: only 3 or 4 provide full support for game controls and touchpads.

So, your main question right now is: I'm gonna play commercial games like Dead Trigger, or I'm gonna play emulators like Fpse?. If you are gonna emulator any custom rom will do, BUT, if you plan to play commercial games, then choose carefully what rom are you going to install.

I try first CM9 using FreeXperia 149 and I hate it, a bit slow, no tethering, no touchpad support. Then I try CM7.2 and it was as fast as it could be, but no touchpads in commercial games. So my choices went to Dixperia 2 or Xperia NXT LE. There was 2 more options, Cola Rom and Gamer 4 Rom, but I didn't try any of these.

Because you are asking for help on CM installation, I will refer only to this, but remember what I said about commercial games.

To install CM on your Xperia PLAY first you need to know if you have a CDMA or a GSM phone. To do such you need to turn off your phone and remove the battery cover. Then you must observe: can you insert a microSD card only?, if so, then you have a CDMA phone. On the contrary, if you can insert another card behind microSD card, then you must have a GSM phone. For reference, Xperia PLAY R800i, R800a, and R800at are all GSM phones, while Xperia PLAY R800x is only CDMA.

Knowing this, you must download CM according to your phone, this ones for GSM, and this ones for CDMA phones.

Optional, you can download Google apps for CM7 or CM9 from here.

You now need to open rom zip and extract boot.img. You need to flash this using fastboot.

Now put rom zip and Google apps zip on microSD card. Reboot in recovery mode. Inside CWM choose "wipe data/factory reset", then "wipe cache partition", and then in advanced options choose "Wipe Dalvik Cache". Then on main menu choose "install zip from sdcard", then "choose zip from sdcard", search for the zip you just download from CM webpage. Repeat steps to install Google Apps, and then reboot.

The very first time will take about 2-3 minutes to start.

Hope this helps.