i. Alloys are a homogeneous mixture of metals or non-metals because
a. It shows the properties of its constituents, and
b. It has variable composition, e.g. brass is considered a mixture because it shows the properties of its constituents, copper and zinc; and it has a variable composition.
ii. No, a solution is not generally a liquid always. For e.g. alloys are known to be solid solutions.
iii. The term solution is generally used for 'true solution'. In this case, the solution is always homogeneous.
In the case of 'colloidal solution', that is not a true solution i.e. the solution is heterogeneous.