there actually is no super saiyan 2 gohan when the time is right gohan goes into saiyan rage mode and beats cell, sorry.
There is a Gt movie called A Hero's Legacy and it is about Goku Jr., and Pan is alive and Goku shows and talks to Goku Jr.
To get the first generator u have 2 left -up-left and then battle android 20 then left-into a tunnel. There arrange the switch as on-off-on-on-off-off then go up u will get a house. Enter the house enter the door on the top left corner you will find the generator