show the changed configurations(not all the configure).
You can do that with
show | compare. If you want to see all changes, make sure you go to the top of the configuration first using
top. If you're already editing a section (for example since you did
edit protocols bgp first) and you run
show | compare you will only see changes in that section.
how can I call off my new changed configurations?
Go to the top of the configuration and then do a rollback to go back to the last saved configuration:
And then quit configuration mode:
Juniper has a free PDF which explains these things and many more CLI related things: Day One: Exploring the Junos CLI.