I think playing a note on a guitar is not difficult because you only need to press a string on a fret to produce a note. It is harder to name or locate a note in the guitar than a piano. But what is hardest in the guitar is memorizing and learning the chords especially the hardest ones.
For beginners, the hardest chord to learn and to master is the F chord. Your index finger must be covering the whole first fret, your middle finger on the A string, 2nd fret, ring finger on the C string, 3rd fret, and your pinky finger on the F string, 3rd fret.
All your fingers will be used in this chord and positioned in a not-so-comfortable manner. Some regular guitar players find this chord still difficult to play especially in fast songs.
In between notes are the notes right after the letter, like A and A#. All the notes on the first string, which are called natural. Natural notes are those without sharps or flats. The best place to begin learning is on the top string. Learn each note individually, as opposed to trying to master the guitar in one day.
Focus on one letter entirely. Build up your speed slowly. The best place to begin learning is on the top string. Try to learn and as much as possible. Focus on one letter repeatedly. Split up into individual notes. Sometimes this can help alleviate confusion while learning the notes.