What's the difference? Help please?

The desktop version and the pocket edition are two different things, I mean they are the same game but both platform (I.E Desktop and phone) it's on are different and are not connected with each other since both platforms are programed specifically to connect with it's own kind (like PC players connect to PC player, Xbox players connects with Xbox players and so on). The versions will always be behind the PC since 《我的世界》 started and risen with the PC it's the most current version as of the Xbox and PE it's several versions behind (since they started later). and your phone crashes and able to transfer question... I can't answer that as I have no knowledge of it.

你 cannot play PE and PC at the same time. But if 你 want to try out the Demo on the PC, try it out, it is for free, but 你 cannot connect with the Full Version PC if 你 want to play multi. The PE, came out like in 2011, whilst the PC came out in 10th May 2009. I tried the Lite edition of the PE (which they don't sell anymore for no reason), it was bad, the 太空 was limited, couldn't get ores etc. But that was the lite version which sucked... Maybe this could help somehow!