[Samsung Galaxy Player 4.0, 5.0] zeroxia:
Well I figured out... It turns out after flashing the "preflash" zip, you MUST NOT reboot, but instead go on to flash the ROM itself.

And another important thing: you must restore /efs after flashing back to stock using Odin.

Initially I just can't get such hints from all those ROM threads in the development forum. Maybe it's too obvious. But it certainly is not so obvious for we Chinese people, as I searched in Chinese, I can find many have done exactly the same I did (lol). Anyway from the Chinese forums I finally get to it.

I have made a record of all the flashing procedures and put it here, hope it will help some avoid searching all over the world to get started from scratch.

Samsung Galaxy S Player WLAN 4.0, YP-G1 International (Intl.) version flashing notes

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I use Windows 7 X64 to perform the following operations.

Part 0: Backup /efs (to your computer)

I don't know what this really means, but it is REQUIRED for later flashing, so don't rush to the flashing.

I use adb shell to make backup:

# tar cf /sdcard/efs.tar /efs

And pull it to your PC and keep it safe:

C:\> adb pull /sdcard/efs.tar .

(This is just an example, your backup and restore approach can be different)

Part 1: Revert to stock Android 2.3 (Gingerbread)

I believe this can be performed as long as you have download mode available, and this should be a good start if you think you have totally messed up with your device.

Files you need:

a. Samsung mobile driver: http://xdaforums.com/showthread.php?t=2038555

For the 1.5.25.0 driver installation, the install wizard says it some error occurred at the end. But it seems no harm.

b. Odin flashing tool: (download link is the same as a.) I use Odin 1.85 for the YP-G1 device.

c. The 2.3.6 stock ROM: http://xdaforums.com/showthread.php?t=1531850

I picked G1XXKPQ, version 2.3.6. Since my device is bought from China, it is compatible.

Also download the "Pit" file, again for my YP-G1 from China, I choose the "Intl" version.

Steps:

1. Put your device into download mode:

a. Shutdown deivce entirely, and pull battery and re-install to be sure

b. Key combinations: PRESS and HOLD: HOME button and Volume Down button. Then additionally, press and hold POWER until "Download mode" appears on device screen.

2. Connect your device to PC, let the system recognize new devices and install drivers.

3. To further make sure, you can disconnect the device, pull out its battery. And enter download mode, then connect to PC again.

4. Open Odin tool, this needs Administrator privilege, if Odin detects your device, it will display some message like "<ID:0/008> Added!!", and there is a blank text field under the "ID:COM" label turning to yellow color and showing a COM port number.

Then on the Odin GUI, select two files:

a. Click "PIT" button, locate your downloaded ".pit" file. This will cause the "Re-Partition" option to be selected automatically.

b. Click "PDA" button, locate your ROM, which is a .tar.md5 file, like: YP-G1FullRestoreIntl2.3.6.tar.md5

c. Click "Start" and wait until the device reboots.

Sometimes Odin is stuck at "SetupConnection", then retry: find a better cable (should not be too long), find a better USB port on your PC (USB 2.0 possibly can be preferred over USB 3.0). Retry by restarting from Step 1.

5. After device reboots, it enters the Android recovery automatically, and you can see some RED text saying "mount failed" alike. Just choose "wipe data/factory reset" and then reboot.

Now you are stock.

Part 2: The TerraSilent custom kernel (with custom recovery ClockWork Mode, CWM)

The stock Android recovery cannot be used to flash custom stuff, so you need to flash a custom recovery first.

Steps:

1. Download TerraSilent custom kernel: http://xdaforums.com/showthread.php?t=1643384

I choose 1.3.5, which comes with CWM v5.0.2.7

The odin flashable kernel file is: TerraSilent_intl-1.3.5.tar

2. Shutdown device, and enter download mode again, and connect it to the PC, open up Odin, DO NOT touch the "PIT" button, only the PDA button, and choose custom kernel file. Then punch "Start".

3. This should be quick, and device reboots automatically, but you will find nothing new in your stock Gingerbread ROM.

Part 3: Restore your /efs folder

Like part 0:

C:\> adb push efs.tar /sdcard/

Then "adb shell" to the device, and "su" if necessary:

# tar xf /sdcard/efs.tar -C /

(Again your restore approach can be different)

Part 4: Get 4.x AOSP ROM and flash:

This is the time you transform your Android 2.3 player into an AOSP based Android 4.x ROM, so it's a little tricky (in fact the tricky stuff includes above /efs backup & restore thing)

I'm taking this CM9 as an example: http://xdaforums.com/showthread.php?t=2213152

Because in this thread it mentions you MUST restore /efs for this ROM install to succeed, otherwise it will fail. (I have attached a photo of the failed install for reference.)

1. From this thread, download two files:

a. cm-9-20130402-kernel-preflash.zip

b. cm-9-20130408-UNOFFICIAL-ypg1.zip

Put both to device's /sdcard. And REMOVE your external Micro SD card if any.

2. Shutdown your device. Addtionally pull and re-install the battery for sure. Then you need to enter the recovery.

The key combinatoins for entering recovery:

PRESS and HOLD: HOME button and VOLUME UP button.

Additionally, press and hold power button. When the screen lights up, release POWER button, but keep HOME and VOLUME UP pressed.

As you are in the CWM recovery, this is from the TerraSilent custom kernel, version is v5.0.2.7.

a. Perform some wiping:

- wipe data/factory reset

- wipe cache partition

- advanced, - Wipe Dalvik Cache

b. Then install:

- install zip from sdcard, - choose zip from sdcard, --> select the .zip ROM file and confirm.

Sometimes the /sdcard won't mount, i.e., after choosing "- choose zip from sdcard", nothing can be found there.

Then I pull the battery and repeat it. Probably the files will show up.

Flash in the following order, don't reboot after the first .zip is flashed:

a. cm-9-20130402-kernel-preflash.zip

b. cm-9-20130408-UNOFFICIAL-ypg1.zip

When flashing the second one, the device will reboot automatically. Wait patiently until the device stays at a "new" custom recovery, which shows its version as "CWM-based recovery v6.0.1.2". Then you have completed all. Here you can flash the GAPPS package, if you have put it at your /sdcard before.

PS. "GAPPS" packges download: http://goo.im/gapps/

Please match the version, e.g., CM10.1 is "Jelly Bean" 4.2 (JB), CM9 is "Ice Cream Sandwich" (ICS).

Part 5: Other AOSP based ROMS.

From now on, you don't need that "cm-9-20130402-kernel-preflash.zip" file when flashing other AOSP based ROMS.

Just put the .zip ROM file at /sdcard, and reboot into custom recovery, wipe as needed, and install.

Attached is a photo showing how it fails to install the CM9 ROM if /efs was not restored: