In advanced English morphosyntax and categorical lexical analysis, identifying parts of speech frequently depends on syntactic distribution, valency, and functional shift rather than isolated semantic definitions. Consider the following four advanced propositions regarding nouns, pronouns, adjectives, and adverbs: I. A word that functions prototypically as an adjective in one context (e.g., 'direct' in 'a direct route') can undergo zero-derivation (functional conversion) to operate as a flat adverb of manner without morphological suffixation (-ly), maintaining identical form while shifting its modification from a nominal head to a verbal head (e.g., 'She flew direct to London'). II. The indefinite pronoun 'one' possesses distinct pronominal properties enabling it to head noun phrases independently; however, unlike traditional personal pronouns, 'one' cannot function as a generic third-person pronoun, nor can it serve as a prop-word substituting for an entire nominal projection containing an adjective head (e.g., *'I lost my blue pen and bought a new one'*). III. Intensive and reflexive pronouns share identical morphological suffixes ('-self' / '-selves'), but they are syntactically distinct: reflexive pronouns are argument-bound anaphors required by the valency of the governing predicate where the antecedent and the object occupy distinct theta-roles within the same clause, whereas intensive pronouns are non-argument adjuncts (appositive nominal modifiers) that emphasize a referent and can be omitted without violating core clause grammaticality. IV. When an -ing participle form appears pre-nominally preceding a noun, it invariably functions as an attributive adjective if it admits degree modification by intensifying adverbs such as 'very' or 'more' (e.g., 'a very surprising development'), whereas if it retains pure verbal government and takes a direct object complement, it must be analyzed syntactically as a gerundial noun or participial adjunct outside the core adjectival category. Identify the option that correctly evaluates the morphosyntactic, categorical, and theoretical validity of propositions I, II, III, and IV according to standard English grammar.