Another OS is installed on this device by default. The maximum Android OS that is possible is version 4.x. The performance did not suit me at all for 70.- and I could not install any channels. Conclusion: I threw the money out the window and ended up replacing it with a more expensive Apple TV.
Yes, this is possible. It is not specified by the manufacturer. The supported file formats are FAT16/32, NTFS (read only), NFS, Ext2, Ext3. If ever I suggest you use Ext2 or Ext3.