@Madham

I just know a way for chips with v1.1 loader and it would be a oneway trip unless you upload some modified loader.

For v2.31 i could not find a way to change the loader. I dont want to post here details, because they will be most likely deleted.

Leave a email address here and i will contact you. You may also search at youtube or use google.

One more thing:

For changing the option to use P1.5 you need to start the loader by hardware condition. A LCALL 0x3800 somewhere in your app wont do the job, and you also have to do some download. This is  because the bootloader seg is writeprotected when regular code is executed. 

After that the bootloader will start when when you pull P1.5 low during a power on reset.

Hello, how do you determine the current boot version of the chip? Is it because all of your 2.31 chips do not support pin configuration? How did you do the pin configuration? In theory, boot pin configuration is supported after 2.31. If not, could you please send us a piece or two for us to try? Or repurchase the 2.40 version of the chip to test it.