There are four main differences: PPI, the number of reading lights, whether it is waterproof or not, and memory.
Ppi: The ppi of the classic version and the exclusive version is 300, while the ppi of the youth version is only 167. The ppi is higher, the text is sharper and clearer, and it looks more comfortable.
Number of reading lamps: The number of reading lamps for Youth Edition, Classic Edition and Privileged Edition is 4, 5 and 25 respectively. The more desk lamps, the more uniform and soft the light.
Waterproof: the youth version is not waterproof, but the classic version and the exclusive version are waterproof.
Memory: There is little difference between the classic version and the exclusive version, which are 8GB/32GB respectively, and the youth version is 4GB.