$1)$
$*)A:\begin{cases}H_2:x mol \\ C_2H_2:y mol \end{cases}\Rightarrow \begin{cases}\frac{2x+26y}{x+y}=2.5 \\ x+y=\frac{20,16}{22,4} \end{cases}\Rightarrow \begin{cases}x=0,6 \\ y=0,3 \end{cases}\Rightarrow \begin{cases}\%V_{H_2}=66,67\% \\ \%V_{C_2H_2}=33,33\% \end{cases}$$*)n_{H_2 pu}=n_A-n_B=\frac{20,16-10,08}{22,4}=0,45 mol$
$\Rightarrow n_{H_2 du}=0,6-0,45=0,15 mol\Rightarrow C:\begin{cases}H_2:0,15 mol \\ C_2H_6:(\frac{7,392}{22,4}-0,15)=0,18 mol \end{cases}$
$\Rightarrow C:\begin{cases}\%V_{H_2}=45,46\% \\ \%V_{C_2H_6}=54,54\% \end{cases}$
$*)B:\begin{cases}H_2:0,15 mol \\ C_2H_6:0,18 mol\\C_2H_2:a mol\\C_2H_4:b mol \end{cases}\Rightarrow \begin{cases}a+b=0,3-0,18 \\ b=n_{H_2 pu}-2n_{C_2H_6} \end{cases}\Rightarrow \begin{cases}a=0,03 mol \\ b=0,09 mol \end{cases}$
$\Rightarrow B:\begin{cases}\%V_{H_2}=33,33\% \\ \%V_{C_2H_6}=40\%\\\%V_{C_2H_2}=6,67\%\\\%V_{C_2H_4}=20\% \end{cases}$
$2)m=0,03.26+0,09.28=3,3 gam$