Hello Hasib!
I would say that #1 & #2 are correct.
But the rest of the sentences should be written like this:
3. At the last moment, they chickened out for fear of getting beaten.
4. At the last moment, they chickened out because they feared getting beaten.
5. At the last moment, they chickened out fear of getting beaten.
In #3 & #5 "for fear of" is the same as "because they feared"
I hope that helps!