difference between named for and named after idioms

[Meerak869]

The Bunsen burner, named after the German scientist who improved its design and efficiency, was invented in 1885 not by Bunsen himself but by fellow scientist Michael Faraday.

a. named after the German scientist who improved its design and efficiency, was invented in 1885 not by Bunsen himself but by fellow scientist Michael Faraday

b. which was named for the German scientist who improved its design and efficiency, was not invented in 1885 by Bunsen himself but, rather, by Michael Faraday, his fellow scientist

c. which is named for the German scientist improving its design and efficiency, was invented not by Bunsen himself but, rather, by Michael Faraday, a fellow scientist in 1885

d. named for the German scientist improving its design and efficiency, was not invented by Bunsen himself but by Michael Faraday, a fellow scientist, in 1885

e. naming after the German scientist who had improved its design and efficiency, was invented not by Bunsen himself, but, rather, by fellow scientist Michael Faraday in 1885

The original sentence is correct. The contrast set off by the parallel structures "not … but" should only contrast Bunsen and Faraday; the reference to the year 1885 should not be included in that parallel structure, since the year in which the burner was invented is not part of the indicated contrast. The modifier "in 1885" should be attached as directly as possible to the action "was invented".
The idioms "named for" and "named after" are both correct, so there can be no eliminations based on those idioms.

According me Named after sounds better here. And the option which contains it is the right answer choice A.
But im not sure what can be the scenerio where named for is the right option.
please explain difference between named for and named after idioms in detail.

[RonPurewal]

the answer key means exactly what it says:

The idioms "named for" and "named after" are both correct, so there can be no eliminations based on those idioms.

there is no meaningful difference at all.