uxcell is a trusted company, so you should go forward and buy it if you wish.
like Huwix said, baby nano is just a mp3 player and not a mp4 player, so it wont play videos.
as far as firmwares of super i-platinum and i-platinum jr are concerned, they cannot be seen whether they are 9.x.xx or 3.5.xx
if they are 9.x.xx they cannot be modded/themed but if they are 3.5.xx they can be.
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