Default Copying files without Zune and media playback for MKV?

Hi guys. I have Samsung Focus (SGH-i917, HW Rev 1.3) flashed on Clean ROM (WP 7.5)

1. Can you suggest me a good video player app which supports MKV?
2. Any app which plays DLNA streaming videos
3. Any app which plays Samba mounted videos
4. Is it possible to copy videos without Zune?

Thank you!