I was writing a story.
I have written poems.
I have been writing a novel.
I had written a song.
<span>I had been written up for fighting.
</span>
The last one is sort of weird, since you can't say "I had been written" in the sense of the verb "write" as it would be grammatically incorrect.
Human limitations are the limits to yourself and your body.
Possibilities are the things you could potentially do but are not.
If you want examples then please ask this question again.