Which of the following is not a member of the same homologous series?

In which of the following reactions does an acid-base reaction take place?

Predict the product of the following reaction: $CH_2=CH-CH_2-CH_2-COOH \xrightarrow{Br_2, NaHCO_3} \text{Product}$

$A$ hydrocarbon $C_5H_8$ consumes two moles of hydrogen. On ozonolysis,it produces $2-$oxopropanal and methanal. The hydrocarbon is:

$1, 2-$dibromocyclooctane $\xrightarrow[\substack{\text{(ii) } NaNH_2 \\ \text{(iii) } Hg^{2+} / H^{+} \\ \text{(iv) } Zn-Hg / H^{+}}]{\text{(i) } KOH \text{ (alc.) }} \underset{\text{(Major product)}}{P}$. $P$ is

Provide a chemical test to distinguish between butane and but-$1$-ene and write the corresponding reactions.