probable
It would most likely be an adjective prepositional phrase because it will modify a noun.
Portable
credible
LUNA
· thrifty
No, it is not an adverb. Crossed is a verb form. It may form a participial phrase which would likely be an adjective phrase.
adjective phrase
believable
Popular
There is no adjective. But the phrase "by the oven" would likely be an adjective prepositional phrase.
It's a phrase such as "they will likely go to the shops" - here, "likely" is behaving as an adverb modifying "will" (equivalent to "probably" in "they will probably go to the shops"). "Likely" is more often - and, in my opinion, more correctly - used as an adjective: "It is likely that they will go to the shops".
An adjective (adjectival) phrase modifies nouns or pronouns. There are several types, including those based on an adjective (adjective and its adverbs), as well as adjective prepositional phrases, and infinitive phrases.