Посмотрите TOS
https://www.upwork.com/legal#registration, там явно указано, что годиков должно быть более 18.
You also promise that you are eligible to enter into this Agreement, including because you are 18 years or older.
Upwork offers the Services for your business purposes only and not for personal or consumer use. By registering for an Account or by using our Services, you represent that you: .... (d) are either a legal entity or an individual who is at least 18 years old (or the age of majority in your country if the age of majority is over 18), and that you can form legally binding contracts.
Обходить не рекомендуется, можно словить пожизненный бан. Думаю, вас даже до верификации не допустят, изучив документы.
Не спешите, дождитесь совершеннолетия :)