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."
comparative
The comparative of "first" is "earlier" or "prior".
comparative
comparative
Comparative silhouetting is a technique used in forensic anthropology to identify the sex of a skeleton by comparing the outlines of specific bones to known standards of male and female anatomy. By analyzing the differences in bone shapes and proportions, researchers can make an educated guess about the sex of the individual.
comparative
His is a possessive pronoun and, as such, does not have a comparative form.