Thanks to the ingenuous identification of Apollinaris with the subject of a headless inscription found in Asia Minor by Werner Eck, we know most of the earliest steps of his cursus honorum.
After concluding his command of Legio VI Ferrata, Apollinaris returned to Rome to serve as prefect of the aerarium militare for three years.
In a letter to Quadratus (Epistulae, IX.13), Pliny recalls his prosecution after the assassination of Domitian of the delator or informer Publicius Certus.
One of the five senators who had spoken against this prosecution was Apollinaris; Pliny's description of him as "consul designate" firmly places it in this period.
Although the emperor Nerva failed to act on the motion to prosecute, Certus was passed over in consideration for a consulship, and in any event fell ill and died soon afterwards.
The existing letter is a reply to explain his estate is located in a desirable region of Etruria, and includes an extensive description of Pliny's villa at Tifernum (the modern Città di Castello).