Which of the following are constitutional isomers of heptane?

I'd rather give an incomplete correct answer than a complete answer that may be incorrect. In the first group keep in mind the formula must be the same - C7H16. Thus we reject pentane (C5), hexane (C6), and 2-methylpentane (C6) as candidates. I believe all the remaining compounds are constitutional isomers [see 1st reference].
 In the second group cis-trans relations of groups in a molecule constrained not to rotate by a double bond would eliminate 2,3-dimethyl butane and 1-hexene which can rotate. I believe the remaining compounds have cis and trans isomers.
 A reference is given for the third set which I shall not speculate about.