An alkyne shows acidic nature only if it contains terminal hydrogen.
CH₃ - CH₂ - C \(\equiv \) CH + 2AgNO₃ + 2NH₄OH \(\rightarrow\) CH₃ - CH₂ - C \(\equiv \) C - Ag + 2NH₄NO₃ + 2H₂O
        1 - butyne                                                    Silver butynide
CH₃ - C \(\equiv \) C - CH₃ + 2AgNO₃ + 2NH₄OH \(\rightarrow\) No Reaction due to absence of acidic hydrogen

(i)\({ CH }_{ 3 }-\overset { \overset { { CH }_{ 3 } }{ | } }{ { CH }-\underset { \overset { | }{ { CH }_{ 3 } } }{ CH } - } CH_{ 2 }-{ CH }_{ 2 }-\overset { \overset { { CH }_{ 2 }-\overset { \underset { | }{ { CH }_{ 3 } } }{ CH } -{ CH }_{ 3 } }{ | } }{ CH- } { CH }_{ 2 }-{ CH }_{ 2 }-{ CH }_{ 2 }-{ CH }_{ 3 }\)
(ii) 

(iii) \({ CH }_{ 3 }-\underset { \underset { { CH }_{ 3 } }{ | } }{ CH } -{ CH }_{ 2 }-{ CH }_{ 2 }-\underset { \overset { | }{ \overset { CH-CH_{ 3 } }{ \overset { | }{ { H }_{ 3 }C-CH-{ CH }_{ 3 } } } } }{ CH } -{ CH }_{ 2 }-{ CH }_{ 2 }-{ CH }_{ 2 }-{ CH }_{ 3 }\)

Markovnikoff's rule: "When an unsymmetrical alkene reacts with hydrogen halide, the hydrogen adds to the carbon that has more number of hydrogen and halogen add to the carbon having fewer hydrogen".
Eg: Addition HBr to unsymmetrical alkene: In the addition of hydrogen halide to an unsymmetrical alkene, two products are obtained.

Conformations of n-Butane: n-Butane may be considered as a derivative of ethane, as one hydrogen on each carbon is replaced by a methyl group
Eclipsed conformation: In this conformation, the distance between the two methyl group is minimum. So there is maximum repulsion between them and it is the least stable conformer.
Anti or staggered form: In this conformation, the distance between the two methyl groups is maximum and so there is minimum repulsion between them. And it is the most stable conformer.