Word Usage – Difference Between ‘Left’ vs. ‘Left from’

In your first example, you would just use above, as an adverb is all that is needed. But it really only describes what is directly above.

In your second example, from above is not helpful because it is not specific as to what you are referring to. You should point to the specific location.

When using from above, from is a preposition, so I expect an object in that phrase. For example:

From above the trees, I could see the distant horizon.

The locations are specific. Also motion is often involved:

The birds flew from above the trees to the roof of our house.

There are some idiomatic usages though, for example:

Their new baby was a gift from above. (meaning from heaven)

Computer systems like Stack Exchange or Facebook are stupid and are (generally) programmed to always round down to full hour increments regardless of the proximity to the subsequent hour.

As such, it's necessary to ascertain the actual time the post was made if you really want to know how long ago it is.

In actual usage, no human would say that something one hour and fifty minutes ago happened "one hour ago". We are smart and know that one hour and fifty minutes is nearly two hours so we either round up to "two hours" or we say "almost two hours ago".

Generally, at the very least, we go in half-hour increments. So, something that happened an hour and thirty minutes ago is "an hour and a half ago". We distinguish events that didn't quite meet that time frame by using "less/more than" or "about" or other words that note that the time is imprecise.

In practice, people may be as precise as rounding to every ten minutes... so if something happened one hour and 42 minutes ago, they might say "about an hour and forty minutes ago" they might also go to the quarter hour "about an hour and three quarters ago" or to the full hour, "almost two hours ago". All of them are valid. I attest that it would be considered rather unusual to say "one hour ago" in this case.