I think, you can't upgrade it via web. You should start tftp server - 192.168.0.225 and name the file as: tp_recovery.bin - it should be factory file. Then:
- disconnect power supply
- press and hold wps/reset button
- connect power supply and wait until one of diode start blinking
- release wps/reset button
- wait until update is installed.
Before doing this, you should have backup of working router soft.