In Nicholas J. Brown's book, The New Penguin Russian Course - A Complete Course for Beginners (1996), there is an exercise (27.5 if it matters) containing a sentence;
Девяносто пять процентов тех, кто участвовал в опросе, назвали Кларка Гейбла единственно возможным Реттом Батлером.
I. I assume that the last four words are in instrumental case because it is like a profession, to be this Ретт Батлер. (Question 1)
As it is written...
II. I believe that the two words I am inquiring about , единственно возможным (Реттом)..., are an adverb, followed by a long-form adjective used attributively. (Question 2)
I don't see a 'linking verb' so I assume that the adjective 'possible' is used attributively. (Question 3)
I can see that the adverb 'only' is modifying the following long-form adjective 'possible', but what would it mean if the adverb was replaced by a short-form adjective (I think two consecutive adjectives used attributively, maybe even predicatively, require the first adjective to be short-form. (Question 4)), therefore modifying the same noun 'possible' modifies, as in the following?
единственен возможным (Реттом Батлером)...
Since short-form adjectives are only used predicatively, would this be valid as there seemingly is no linking verb? (Question 5)
If I wrote it from scratch...
If I was going to make the sentence from scratch, can't both consecutive words единственно возможным actually be constructed attributively, as long-form adjectives (Question 6) and written as
_единственным возможным (Реттом Батлером)..._,
as they both precede the noun (Ретт(ом) Батлер(ом)) they modify? (Question 7)
By this site, when to use the short form of an adjective?, I understand the temporal/permanence features of the long and short adjectives, and so there may be more permanence with 'only' in this case. (Question 8)