if anyone want change opera user-agent:
1)go to opera:config
2)search word "user"
3)scroll to "spoof user agent id" and set:
- 1 = Opera
- 2 = Mozilla
- 3 = Internet Explorer
Site-specific values:
- 4 = Mozilla, Opera not mentioned
- 5 = Internet Explorer, Opera not mentioned

4)restart opera
i used "2" and work fine now but the 1st time I try didn't work.
if don't work the 1st time you can try:
-go to opera:config again
-set "user js storage quota" on 1
-close opera
-go to config again
-set again "spoof user agent"
-close and restart opera

it's work fine for me

someone asked for url filter: i see it in config under network (if you set search-word "user" you should find it.