This may be what the OP was asking. Italics are my editing.
acceptable and possible to write a character where there is no effort to hide said character's failures and weaknesses, while
displaying their character development slowly? I am not planning on writing a long series. Also I wonder, can a writer
display character growth realistically
as a step backward as well as forward?
For the first question it depends on the character. Usually it is a yes, but for some types of characters like the Magnificent Bastard
you might not want to show as many of their weaknesses as say the protagonist.
For the second question I'm not sure, because I haven't tried that. I'm sure other tropers may be able to help you out.
Has ADD, plays World of Tanks, thinks up crazy ideas like children making spaceships for Hitler. Occasionally writes them down.