Can a 16 year old student pilot "pre-take" the checkride?
14 CFR Part 61.39 (a)(5) states that you can not take a checkride in the US until you are of age to hold the desired certificate.

(5) Meet the prescribed age requirement of this part for the issuance of the certificate or rating sought;

Sorry. I encourage you to take as many mock-checkrides as possible in the meantime.
Also, in addition to mock-checkrides. You can train for your instrument rating. 14 CFR Part 61.65 allows you to take a combined checkride or even back-to-back private and instrument checkrides.
§61.65 Instrument rating requirements.
(a) General. A person who applies for an instrument rating must:
(1) Hold at least a current private pilot certificate, or be concurrently applying for a private pilot certificate, with an airplane, helicopter, or powered-lift rating appropriate to the instrument rating sought;