1. When you select songs using the Database, Rockbox creates a playlist for you. This is known as a dynamic playlist. When you select a different song using the database, Rockbox will warn you before erasing the existing playlist and starting a new one.
If you would like to turn this feature off, you can do so using the following setting:
Main Menu --> Playlist Options --> Warn When Erasing Dynamic Playlist --> No
If you want to keep this warning, just press the Select button when instructed to do so. (As I'm sure you're aware from reading the Rockbox Manual, the "Select" button is the center button on your iPod.)
2. As for your other question:
My main question is where is the [path] that is showed in the ID3 tags info?
For example, where is:
/iPod/Control/Music/F29/NFQC.mp3
You have apparently loaded your music through iTunes. iTunes renames your files and puts them into random directories. (You can get some more information in
this FAQ).
You can avoid this by simply dragging and dropping music onto your player. If you do so, however, the music will be available only to Rockbox. The original firmware will not recognize it.