Most of your questions about SIFF and Battle of the Bands can be answered in either of these two documents:

BATTLE OF THE BANDS INFORMATION PACKET

SIFF INFORMATION PACKET

If you still have any questions after reading these, please post your questions in this thread.

I wanna participate, but I have a question. I'm going to make a video with a story, but this video won't have subtitles or voice actors (only music and sound effects). Is this a film or a music video? 

I don't know without seeing it. Does it fit the definition of a music video?

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Music Video - 

noun

a commercial videotape featuring a performance of a popular song, often through a stylized dramatization by the performers with lip-synching and special effects.

Luza, I will add to this answer too because this sounds like my style of machinima. I usually create a story that is told by the words of a song, but it is not really a music video by my view of it. So ya, if in your mind it is a film - a story told by lyrics of music instead of voice acting or subtitles, then film it is.  I will indulge with my example.

https://www.youtube.com/watch?v=xUMoqF2BGEs

My poster is smaller than everyone elses. Do you know what I did wrong?

I can't find your poster in the gallery to tell you what went wrong.  If you created it using the size guidelines we laid out in the poster/film trailer thread, there shouldn't be a problem.