There are circumstances when Solar PV is not suitable for a roof, for example, if your property is listed, your roof is heavily shaded, or your roof is just not big enough. It can also be a preferred choice too.
Ground Mounts can be secured into the ground using a galvanised ground screw (which winds into the earth) or it can be secured using concrete, depending on the type of ground, (for example if it is stony). This is an example of a ground screw system. Read more...
Usually up to 100 metres (329ft). Any further than this will be dependent on communications and budget, in terms of armoured cabling and civil works, which can then become cost prohibitive.