To solve this problem, we need to match each compound in List-I with its corresponding property in List-II.$\\$Let's analyze each compound:$\\$(a) $$MgH$_2: \\$• Magnesium hydride is an ionic compound because it consists of $$Mg$^{2+}$ and $$H$^{-}$ ions.$\\$• Therefore, it is best matched with (iv) Ionic.$\\$(b) $$GeH$_4: \\$• Germanium hydride is similar to methane (CH$_4$) in structure, having a tetrahedral geometry.$\\$• It has a complete octet and no lone pairs, making it electron precise.$\\$• Therefore, it is best matched with (i) Electron precise.$\\$(c) $$B$_2$H$_6: \\$• Diborane is known for having an electron-deficient structure due to the presence of three-center two-electron bonds (banana bonds).$\\$• Therefore, it is best matched with (ii) Electron deficient.$\\$(d) $$HF:$\\$• Hydrogen fluoride is a polar covalent molecule with a lone pair on fluorine, making it electron rich.$\\$• Therefore, it is best matched with (iii) Electron rich.$\\$Based on the analysis, the correct matches are:$\\$a$\rightarrow$(iv), b$\rightarrow$(i), c$\rightarrow$(ii), d$\rightarrow$(iii)$\\$Thus, the correct option is Option 1.