Word Difference – Difference Between ‘To Find an Answer to It’ and ‘To Find an Answer of It’

Formally, we use accuse with an act—we assert that somebody did something reprehensible:

Mary accuses John of failing to lock the door.

But we use blame with the outcome—we assert somebody's responsibility for the undesirable result:

Mary blames John for the robbery. OR
Mary blames the robbery on John.

Informally, however, these distinctions often blur. For instance, if the robbery has already been mentioned, blame may very easily take a for clause which explains why the target is blamed:

Mary's house has been robbed. Mary blames John, for failing [=because he failed] to lock the door.

And accuse may take a complement which expresses a state rather than an act:

Mary accuses John of being responsible for the robbery.

Semantically they're very similar, but syntactically, the difference is that underlying is an adjective, whereas underneath is either a preposition or an adverb.

The syntactic difference means that, like most adjectives, underlying usually occurs before the noun it modifies...

This sentence illustrates my underlying point.

...but note that we can also use it as a "continuous verb form", with "point" as the subject...

The point underlying that sentence is made again here.

Apart from that syntactic difference, note that the relatively less common underlying usually refers to something fundamental, that underpins something else, whereas underneath (and plain under) merely implies something being (physical or figuratively) below something else.