I just got my TI nspire cx for school and I really want to run ndless on it, but it cam with version 3.2.4. I have a little bit experience with android, and I had a small idea, but I don't know if it can work. The idea is to hexdump the old and new boot2 and search for the string of the version. If that does not work, search  the the string of the boot2 version with md5 compression. If that does not work search sha1 and so on. If it really gets found, replace the version string from the old boot2 with a newer one than the new boot2. Then hope, that TI doesn't include another signing of boot2.
This is just an idea. I am really not a security expert and I don't have experience with hacking. Please don't hate me if this idea is stupid.

It is stupid. The boot2 is RSA protected so we can't change it unless we know the key. Plus, the older boot2 that lets you downgrade isn't compatible if your calc revision is J or higher (check the last character in the serial on the back).

Ok I will close the thread