Seems V5.3.0_150513 wont let me connect telnet, even when enable the Chinese option boxes in the web interface. Ah well wasted day then!
Downgrader doesn't work on DS-2CD3132F-IW. But it is recoverable, just put the right .dav from (DS-2CD3XX2 Chinese IPC_R0_CN_STD_5.3.0_150513.zip) file back...