I got a used T-Mobile 8100 from a friend. I use AT&T. I have applied for an unlock code, but decided to upgrade the OS following the instructions on the board.

I did this without a sim card. Everything worked fine, except there is no browser showing. What is up? Will it come in after I unlock the device with the AT&T sim card? Do I need to redo the OS?

Finally, I assume the OS upgrades for 8110, 8120, or 8130 will not work with a 8100?

Go to Options >Advanced Options >Host Routing Table >Menu Key >Register Now.

Wirelessly posted (8300: BlackBerry8300/4.2.2 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/102)

I think you need a sim card before the above procedure would work. As to the os question you are correct.