In 1. your second example is wrong.
Utterly is in an unnatural position. Also, we would not say that someone has been concentrated. It's not idiomatic. Someone has concentrated on his work.
Apart from this, while utterly is possible, it doesn't fit naturally in front of concentrated. If you had to use a modifier here, totally is more natural and you would need to omit only.
So, your first sentence should read either:
Ben has concentrated only on his work for several months.
Ben has concentrated totally on his work for several months.
Your second examples are also problematic.
To begin with, literally doesn't fit in this context. Literally is used when someone means that his/her words are exactly true rather than being metaphorical, as in: They were frozen stiff when they were found. Literally, this would apply to bodies and not just to people who were cold.
Moreover, to answer literally means to answer in a literal manner, which is not what you intend.
To literally answer all the questions is trying to emphasise Tom's accomplishments.
So: >Tom has literally answered all the questions correctly is possible although literally serves little purpose here unless you are implying that it was a great accomplishment.