For example, the word "averse" could serve as both a verb and an adjective. Can I still use "aversed" as an adjective? Are "more aversed" and "more averse" the same thing?
For another example, are "more cleaned" and "cleaner" both good grammar and meaning the same thing?
We are talking about adjective/verb pairs such that the adjective form is the same as the base form of the verb. Examples include clean (I cleaned the house/the house is clean), faint (He is about to faint/That sound is too faint to hear), prompt (I have to prompt you to do that/He is always prompt), and others. Let's call such words ‘adjectiverbs’ (following Archive.org: Oxford Dictionaries blog).
Whether you can use the past participle of any verb (adjectiverb or not) as an adjective will vary from case to case. If you can, then whether such an adjective is gradeable (i.e. allows modification by more and the most) will also vary from case to case. Furthermore, in the particular case of adjectiverbs, if the past participle can function as an adjective, it will not generally be interchangeable with the base form adjective.
In short:
For verbs in general (regardless of whether or not they are adjectiverbs), the past participle form of the verb may or may not be usable as an adjective. For example, worried (the past participle of to worry) is usable as an adjective, but heard (the past participle of to hear) is not; see below.
For adjectiverbs, if the past participle form of the verb is usable as an adjective (e.g. cleaned), it is generally not interchangeable with the adjective that looks like the verb in its base form (clean). For example, it wouldn't make sense to replace clean by cleaned in the following sentence: Some things are clean because they were never dirty in the first place. The reason is that cleaned suggests that some cleansing action had taken place, whereas clean doesn't necessarily.
As far as gradeability (clean/cleaner/cleanest), note that, in general, not all adjectives are gradeable. In the case of adjectiverbs, it is not clear if gradeability of one kind of adjective (say, the one that looks like the base form of the verb, e.g. clean) implies anything about the gradeability of the other kind (the one that looks like the past participle form of the verb, e.g. cleaned). For example, if fainted is an adjective (although it might not be; see below), it is not gradeable, whereas the adjective faint certainly is (a fainter sound).
Note that the verb to averse is listed in the Oxford English Dictionary (OED) as 'obsolete'; for what it's worth, its meaning is to turn away. Here are some better examples of adjectiverbs (from this list). For all of them, the verb etymologically derives from the adjective (see the preceding link).
prompt second slow mellow moderate
ready clear smooth quiet blunt
dull round shy complete clean
approximate narrow dizzy faint fit
Preliminary remarks: verbs vs adjectives
One general note on verbs and adjectives: for some verbs, the past-participle (and/or present-participle) form of the verb can function as an adjective, while for other verbs it cannot and has the passive meaning. The ultimate test that enables one to decide whether such a participle-like form can or cannot function as an adjective is whether it can function as a predicative complement (PC).
For example, consider the following pair of expressions (CGEL, p. 541):
[1] a. a rarely heard work by Purcell
b. her very worried parents
To test whether the boldfaced words are adjectives or verbs, we try to make them work as PCs of some verb other than be, such as seem, become, or appear. (This test would be inconclusive with be because in that case the resulting expression could be acceptable simply because it may be interpretable as a passive voice construction.)
[2] a. *the work by Purcell seems heard
b. her parents seem worried
[2a] is unacceptable, and so heard cannot be interpreted as an adjective. In contrast, [2b] is acceptable, and so worried is an adjective. Further evidence that worried is an adjective is that it allows modification by very, as in [1b]. (On the other hand, *a very heard work by Purcell is not acceptable.)
Worried is even gradeable: her parents seemed more worried than usual. However, not all adjectives are gradeable, so lack of gradeability is not good evidence that something is not an adjective.
Three specific examples of 'adjectiverbs'
Prompt
As a verb, to prompt has several related meanings. One is to cause or bring about (an action or feeling); another, to prompt someone to/to do something is to cause someone to take a course of action; yet another, to encourage (a hesitating speaker) to say something, or supply a forgotten word or line to (an actor) during the performance of a play; and finally, there is a meaning connected to a computer requesting input from (a user). (See here.)
As an adjective, however, its meaning is very different: done without delay; immediate. This even though etymologically, the verb prompt is ('apparently', according to the OED) derived from the adjective prompt.
Now we consider prompted. The first question is whether this can function as an adjective at all. Well, a search of google books for e.g. "seem prompted to" returns numerous hits, such as
[3] I seemed prompted to investigate further. (source)
Thus, prompted can indeed function as an adjective (and it is even listed as such in the OED).
But the adjectives prompted and prompt are not at all equivalent: their meanings are different. If I am prompt, that means I do things without delay; but if I am prompted, it means that someone or something caused me to act.
Clean
The OED does list cleaned as an adjective, with the meaning freed from dirt, cleansed. In google books, we do find attested examples such as
[4] And when her house was clean and quiet and the air seemed cleaned again, ... her fondness for the family came back. (source)
The adjectives clean and cleaned are much closer in meaning than prompt and prompted, but are arguably not completely equivalent. Cleaned suggests that some cleansing action had occured, whereas clean does not necessarily. In particular, one could not use cleaned in such sentences as
[5] Nothing about coal is clean.
Faint
The adjective faint has the following cluster of meanings: barely perceptible; (of a hope or chance) possible but unlikely; lacking conviction or enthusiasm; (in predicative function only) feeling weak and dizzy and close to losing consciousness.
The verb means to lose consciousness for a short time because of a temporarily insufficient supply of oxygen to the brain (there is also an archaic meaning of grow weak or feeble; decline).
In this case, however, fainted used as an adjective (e.g. seemed/became fainted) is of marginal acceptability. There are some hits for it on google books—predominantly by authors from India, although there are some by others—but it is not listed as an adjective in the OED. In all cases when it is used as an adjective, however, it would seem to refer to the state of being unconscious. So it would not be interchangeable with the adjective faint in e.g. its meaning of barely perceptible. For example, you can say a faint sound, but not *a fainted sound.
