How can we distinguish between a …

The answer to given questions are as follows -
A1 - True solution is a mixture of homogenous particle which dissolve easily making the solution transparent. Colloidal solution is a mixture of heterogeneous mixture, which don't dissolve and hence form translucent or opaque solution.
A2 - In smoke, dispersion medium is gas while dispersed phase is solid.
In fog, dispersion medium is gas while dispersed phase is liquid.
In cloud, dispersion medium is gas while dispersed phase is liquid.
A3 - Colloidal solution is a heterogeneous mixture due to presence of different sized particles present in the solution. The solution appears to be homogenous due to very small size of small particles, which is not visible by naked eye.
A4 - Colloidal solution from given options is - soap + water mixture and fog.