PS4 Questions about music in PS4 Themes and a poll

[Aoi]

I decided to ask few questions in points because it is more readable. My PS4 is on OFW but it doesn't matter.

1. What is a music format used in PS4 themes packages?
2. Are there any 'critical' limitations related to it, e.g. lenght, bitrate etc.?
3. I wonder if default sound theme is a part of 'silent' theme package?
4. Is theme package like a .deb file? If so, it means music file can be extracted and there is a way to move one step forward.
5. If someone is able to extract a music file from theme package is there a chance for upload it?

As I understand themes contain a fragile information but I don't remember the thread and post where I read about it (there is a one about the Earth visualization on PS3 and application to create static themes on PS4) and few others without information I am interested in.

If I found something at my own on the internet I will update this thread.

I appreciate any help or directions and thank you in advance for voting.