"It is altogether fitting and proper that we should do this." - A. Lincoln
Her behavior was unbecoming.
These words are actually listed as adjectives, as is "frozen."
An example of one which is
not separately listed as an adjective is, "inspiring." "Her words were inspiring."
Edit. Woops! MW Unabridged lists it as an adjective. (Not my American Heritage)
So only the ones which are considered to be adjectives may be used as adjectives. How about that?
BTW, in "The explanation was diverging into two ways", "was diverging" is just a conjugated verb. (past progressive??)
Edit again. I've just recently heard that expression tossed around (conjugated verb) and thought I had figured out what it meant. According to the internet it's a bogus term. Sorry.