Thanks for the help and clearing my mistakes. For the first group.
Want to discuss 2nd groupe though.
1. Neither goes with singular meaning i would place Verb "is" in place of "are" to balance the sentence right !
2. Yes in this sentence i find stuck badly
i have read that if a sentence begin with infinite pronoun (in this case ONE), verb should follow with its object of preposition which is in this case is plural ( Of shoes ) and verb "cost" is plural as well. This makes sentence correct.
I don't know if we take pair as our subject then its wrong sentence as you have pointed out.
Please help me out with this confusing problem.
And also in 3rd sentence Story is the subject as its singular and verb is singular as well.