Please Cooperate me, I want understand about this command
Why i use : ^.*get.+.(exe|rar|zip|iso|mp4|mp3|torrent).*$

Do not use it, it is not a correct parameter and should not be used in Layer7 rules.

Still I am not clear about this command:
When this command is essential to use
Why will i use this command can you explain this ?

^.*get.+.().*$

Thanks

This kind of Level 7 matching is from the past. You may find it in old examples and people may still claim that they use it, but it effectively no longer works.