The Lone Turret

Solution 1:

According to the unofficial Half-Life: Portal wiki, yes, it's the same Oracle Turret! The article's overview reads thus:

This Turret made its first appearance during The Courtesy Call chapter, in which it has been seen by Chell and a newly-disengaged Wheatley, laying in a powerless Aperture Science Pipe Network for many years since the Enrichment Center's destruction. The aforementioned tube is layered beside a catwalk leading to a hallway nearing the ruined Central AI Chamber. The Turret, desperate to be saved from the tube, tries to alert Chell for help by asking "Hello?", however Wheatley directs Chell to divert her attention away from the Turret and generally neglecting it. This neglect finally causes the Turret to mention "I'm different..." as the two abandon it. It remains only in silence after this. There is no way to get the turret out of the pipes, even if Chell continues to focus on it.

The Turret, now referred to as the Oracle Turret for its wisdom, is seen for the last time in the chapter The Escape, where it is seen heading towards incineration (referred to as "redemption" by the Announcer) on a conveyor belt consisting of broken Turrets, as seen in the Turret Manufacturing department. When Chell chooses to save it from "redemption", the Turret spouts a variety of cryptic phrases, in a similar vein to the All-Knowing Vortigaunt from Half-Life 2. Some of these phrases reference Cave Johnson's 'Don't Make Lemonade' speech and mentions Johnson's secretary and assistant, Caroline. Once saved, the Oracle Turret cannot accompany the player since the player must pass through an Emancipation Grill before continuing.