can nokia lumia 920 can play video with .flv extenstion

[Aldi Ducon]

is the any app for that?

 

[IC Blues]

Yxplayer wp8 bu there is no trial for that app.
http://www.windowsphone.com/s?appid=dd50db36-7dab-4696-acb4-2f2184cc1dbb

 

[WPhoney]

is the any app for that?

Nowadays, FLVs are mostly used as "containers" for standard MP4 videos. So you could extract the MP4 video from the FLV container before transferring it to the phone. The extraction takes about 20 seconds for a 2-hour video and there's no quality loss whatsoever! To extract the MP4 from the FLV, I created a custom preset for WinFF with the following command line:

-vcodec copy -acodec copy

The extraction can also be done using FFmpeg (with the same command line above) or Avidemux (this approach is likely the easiest one). All 3 programs are freeware!