Is it permissible for a 14-year-old boy to fall in love, and is he held accountable for his actions like a sane, adult person?

If love means establishing an emotional relationship between a young man and a young woman, then this is not among the actions of the people of faith. If the young man has reached 14 years of age, he is legally accountable (mukallaf shar'an), and therefore it is not permissible for him to establish such a relationship. If he has not yet reached puberty, he is close to it, and he must beware of it so as not to fall into what is legally forbidden.