Somewhat of an academic question given the present situation.
Some airlines such as BA historically required a degree (2:1 or higher) and reasonable A level grades (BBC or better) for cadet entry. Others did aptitude testing which required a degree of grey matter to succeed. At the other end of the scale simply a current licence.
SIN, COS, TAN is as difficult as it gets. You need to be comfortable with numbers, and competent at arithmetic. At your age, keep the day job, and go Modular. Obtain a Class One medical as your first action.