The comparative degree of "far" is "farther" when referring to physical distance or "further" when referring to metaphorical distance or degree.
Both farther and further are comparative forms of far. Farther is only used of distance; further can be used in any context.
The comparative form of far is farther or further. Farther relates to physical distance. Further relates to everything else (time, amount etc.)
That depends what you are estimating of them. Their combined length? Their average length? Their comparative distance in centimetres?
There is no comparative of get.
It can be, when it modifies a noun (e.g. a farther distance) as the comparative of the adjective "far."It can also be an adverb (go farther) meaning "further."
The comparative of "first" is "earlier" or "prior".
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The comparative and superlativeforms of grand are: Comparative: grander Superlative: grandest