Which of the following is used for the conversion of $2$-hexyne into $trans$-$2$-hexene?

Complete the following reactions:
$(1)$ $CH \equiv CH + 2H_2 \xrightarrow[523-573 \ K]{Ni} ?$
$(2)$ $CH_3-C \equiv CH + 2H_2 \xrightarrow[or \ Ni, \Delta]{Pd \ or \ Pt} ?$

Which of the following is the most acidic substance?

$CH_{3}-C \equiv CH$ $\xrightarrow{2 HBr}$ $\xrightarrow{H_{2}O} \text{Product}$. The product is:

Which reactant is used to prepare trans alkene from alkyne?

$CH_3-C\equiv CH \xrightarrow{O_3/Zn, H_2O_2} \text{Product}$ The product in the above reaction is