Help me with my new Asus O!Play Air HDP-R3

[mrigor]

Ok, I just bought the player and I hope that somebody can help me.

How can I watch the 720p .Mkv files with .srt subs?
How can I get working youtube to my O!Play?

I have bootcode 18.

Please tell me what is the best PAL firmware for this machine and where and how to install it.

Thank you.