Is my *Sprint* Nexus S 4G locked?

[cluelessn00b]

I bought this used Nexus S 4G which came per-assigned to the Sprint carrier and with Android 4.1.1.

I would like to upgrade it to Android 4.3 per these instructions but the 2nd requirement states that

"The Nexus S must be unlocked from any network carrier or you won't be able to flash the ROM."

Aside from the fact that this a CDMA, not GSM phone (i.e. no SIM), how can I tell if it is locked or unlocked?

Thanks.

 

[breadnatty08]

When you boot the phone, there should be the Google logo and then a little unlocked symbol below it. If you don't see the unlocked symbol, it's still locked.

 

[cluelessn00b]

Thank you! There is no unlocked symbol anywhere in the boot screen. So it is still locked. :-(

I guess my next question would be "is it possible to unlock it? and if so how?" but I believe that merits a separate subject line. I will go check the FAQ and search existing threads first to see if this has already been answered for this particular combo (Nexus S 4G + Sprint + 4.1.1).

Update 1:

Thanks to this Nexus S: All Things Root Guide I found this How to Unlock Nexus S Bootloader Guide which I believe is what I need as a first step to upgrade from Android 4.1.1 to Android 4.3 (CyanogenMod 10.2).

That led me to this great article which describes unlocking as simple as typing (in adb shell?):
[HIGH] fastboot oem unlock[/HIGH]But before going ahead and doing something potentially dangerous like this (?) I need to understand a bit more about fastboot and what it is. So I found this What is fastboot article.

It remains to be seen whether a CDMA Nexus S can be upgraded to Android 4.3 (CyanogenMod 10.2) but I think that I have to go through the unlocking and rooting process first to find out.

Update 2:

Well, I just tried 'fastboot.exe oem unlock' and and I am getting the dreaded stuck on "Waiting for Device".

I can see the device through 'adb devices' and even take screenshots through Eclipse+ADT. So I don't think it's a USB driver issue.

I thought this step would be simple & easy. What was I thinking?


Update 3:

I am essentially experiencing the same difficulties described in this fastboot issues galore thread. 'adb devices' lists my device when OS is fully running but 'fastboot devices' won't list anything while booted into the screen that's displayed when I press the 'volume up'+'power' button:

FASTBOOT MODE
PRODUCT NAME - HERRING
HW VERSION - REV 34
BOOTLOADER VERSION - D720SPALCI
BASEBAND VERSION - D720SPALF2
CARRIER INFO - SPA
SERIAL NUMBER - ***
LOCK STATE - LOCKED

SELECT - VOL UP OR VOL DOWN
EXECUTE - POWER

REBOOT BOOTLOADER
REBOOT
RECOVERY
POWER OFF

[ANDROID LOGO]

USB Control Init
USB Control End

What am I missing?