Is it possible for research paper to have a similarity of 2 out of 100 using iThenticate?
I don't think I've ever seen an iThenticate paper with 2% similarity. Less than 10% is rare enough.

However: so what? Low similarity isn't a problem, only high similarity is. The latter implies plagiarism, but the former ... I can't think of any way the authors can cheat by having low similarity. If it's a fake paper generated by SciGen then perhaps it would have abnormally low similarity, but you've already ruled that out since you understood the paper. It's also presumably possible to force a paper to have low similarity as well, simply by continuously rewriting the parts that iThenticate flags.

I'd assess the paper on its content and not worry about the similarity.