There are several synonyms, all of which are descriptors based on location. They could include the limbus, limbus cornae, the limbus of the cornea, or the corneal limbus, corneal margin or, finally, the sclerocorneal junction.
No, "but" is not an adverb. It is a conjunction, specifically a coordinator (also known as a coordinating conjunction).
No, "about" is a preposition used to indicate a relation to something else. It is not a conjunction, which are words that link words, phrases, or clauses together in a sentence.
someone else asked, too. no.
of higher rank, quality, or importance or better than something else
Indicators
A biconditional is the conjunction of a conditional statement and its converse.
"Along" is a preposition, used to show direction or position in relation to something else. It is not a connective or conjunction, which are words like "and," "but," or "or" that join words or groups of words in a sentence.
The word before can be a conjunction, preposition, or adverb (and more rarely a noun).As a conjunction, it is called a subordinating conjunction and connects dependent clauses to independent clauses.
The title of the novel Lily's Crossing may be both an analogy and a metaphor: not a physical crossing (a location), but the intersection of her life with that of someone else. In that sense it is also a conjunction of sorts (a coming together).
Indicator
I believe that the phrase "as soon as" functions as a subordinate conjunction, much as "when" does. E.g., As soon as he comes,.... vs. When he comes,...
In conjunction with