Yes, a pure Titan can become human again in Attack on Titan, but only by consuming a Titan Shifter (holder of one of the Nine Titans), which transfers the shifter's power and allows the pure Titan to revert to its human form, as seen with Ymir and others. Without eating a shifter, pure Titans remain trapped as mindless titans, with their human essence merged or lost within the titan body, and can only return to human form if the Titan Curse is ended entirely, like at the series' conclusion.
The Curse of Ymir states that Titan shifters can only live for 13 years after inheriting a Titan power. This is because Ymir Fritz, the original Titan, died 13 years after gaining her powers, and all her successors are bound by the same fate. Eren Kruger was aware of this curse and explicitly mentioned it.
Each Titan holder gets13 years because Ymir only had The Founding Titan for 13 years before being killed. Hence why it's called Ymir's curse.
Titans did not possess a complete, functioning digestive tract; they merely had a stomach-like cavity that eventually filled up with what they swallow. After consuming a certain amount, they regurgitated the contents of the cavity before they continued eating more humans.
Because it is impossible for anyone to surpass the Founder, each person who gained the power of the Titans was fated with the "Curse of Ymir" (ユミルの呪い Yumiru no Noroi?), which limited their remaining lifespan to only 13 years after first acquiring it.
On Earth, those are gases, but the extremely cold temperature of Titan, around minus 290 degrees Fahrenheit (F, or minus 180 degrees Celcius), allows them to be liquid as well (and maybe even solid).
The meaning behind the title of the chapter was first alluded to in Chapter 55, where Dot Pixis speaks of the Fritz royal bloodline (later revealed to be a false monarchy) as being "unbroken for over 2000 years." Chapter 86 revealed that the power of the Titans originated from Ymir Fritz, 1,820 years before Grisha ...
Like all slaves of the Eldian tribe, her tongue was cut out when she was captured, though it may have regenerated after acquiring the power of the Titans. In posthumous illustrations depicting Ymir Fritz, she is shown as a young girl wearing white robes.
However, if the Founding Titan is inherited by someone outside of the royal family, the power can still be used if the inheritor is in physical contact with a Titan with royal blood. This is demonstrated when Eren Jaeger temporarily used the Founder's power after striking the hand of Dina Fritz's Pure Titan.
The Hallucigenia (the source of all Titan powers) isn't even dead — it crawls out of Eren's head after the final fight, still alive. The foundation for the Titan system is still very much in place. The only thing that's changed is that Ymir chose to disable it.
Year 845: The Fall of Wall Maria
Marcel is eaten by Ymir's Titan after the first night of their journey, and Ymir regains her humanity after having stolen his Jaw Titan power.
The nine Titan powers were the Founding Titan, the Armored Titan, the Attack Titan, the Beast Titan, the Cart Titan, the Colossus Titan, the Female Titan, the Jaw Titan and the War Hammer Titan.
Hange's death was the most glorious, the death every true fighter desires. I loved her like no other, but I cried for Levi's heart that she broke.
As a "reward" for Ymir's contributions to his empire, Fritz forced Ymir to bear his children, effectively making her a sex slave.
Eren offered her freedom and infinite choices, Ymir doesn't know what to do with this, so she cries.
Ymir was able to transform herself into the Jaw Titan (顎の巨人 Agito no Kyojin?), a 5-meter Titan. She gained this ability after she ate Marcel, a Warrior from Marley, in the year 845.
In the forest, Zeke uses the power of his scream to transform 30 nearby Survey Corps soldiers into Pure Titans. This was possible as these soldiers had previously drunk alcohol laced in his spinal fluid, with military higher-ups having also been served this fluid.
The Curse Of Ymir definitely exists. The Curse Of Ymir is that whoever inherits titan power/becomes a shifter, DIES after 13 years. This is because Ymir's death took place after 13 years of inheriting the Founding Titan. The Curse can be justified by the example of Eren Kruger's words and actions.
Titan, Saturn's largest moon, you could actually fly like a bird. Titan's gravity is just one seventh of earth so with a pair of strap on wings, you'd have enough lift to take off. The only problem? Titan's a bit chilly minus 290 degrees Fahrenheit.
Like Earth, Titan's atmosphere is primarily nitrogen, plus a small amount of methane. It is the sole other place in the solar system known to have an earthlike cycle of liquids raining from clouds, flowing across its surface, filling lakes and seas, and evaporating back into the sky (akin to Earth's water cycle).
The Cart Titan is in no way a weak link, but it can be considered the weakest of the Nine. Held by Pieck Finger for the run of the show, the Cart isn't built for direct combat or known for its overpowering strength. However, it has its own set of unique abilities.