The cartridge can be changed, but we suggest not change it since Seed has been adjust to be the best status based on actual configuration
No, it cannot be
The USB jack is used for Seed to read music in USB disk, please refer to user manual for details
Seed is made of HDF (high density fiber) of birch, Yukari and Poplar tree
Seed support 33, 1/3, and 45 rpm, which are common on market
It support MP3/WMA/AAC/AAC+/ALAC/FLAC/APE/WAV,etc.