Yes, Gandalf is immortal because he is a Maia, a divine spirit from before the world's creation, but his physical body as Gandalf the Grey could be slain, which happened when he fought the Balrog; he was then sent back by a higher power, clothed in white and with increased power, becoming Gandalf the White, to complete his mission. So, while his spirit is eternal, his mortal-seeming form was temporary and replaceable, notes Quora.
As one of the Maiar, he is an immortal spirit from Valinor, but his physical body can be killed.
It's not the years; it's the mileage. Gandalf isn't a Maia in the same way Sauron is. He was sent to middle earth as an old man, so his body is much more real than Sauron's “raiment”. He can't use his power to the same extent, he can't change his forms at will.
It was a special honor granted to him, because he bore the one ring all the way to Mount Doom. He needed healing for his wound from the Morgul blade, and the severe psychological trauma he had from bearing the one ring, that only the undying lands could provide. Sam would later join him after his wife passed away.
It's possible that Gollum's prolonged search for the ring allowed it to maintain a significant power over him, suspending his aging process. In contrast, Bilbo's exposure to the ring's influence waned after he willingly (mostly) relinquished it, allowing his aging to resume more noticeably.
Tolkien's description of Gollum conforms to a Catholic – and Thomistic – account of envy, which is a “sadness of the soul”; and it is Gollum's unbearable sadness and his unquenchable desire for the one Ring that marks his character.
Because of their contribution to destroying the One Ring, saving Middle Earth and averting Sauron's eventual war on the Valar, they are granted the privilege of seeing the Undying Lands.
Even at his fullest, Olorin/Gandalf was not the equal of Mairon/Sauron, not even close. Same goes for the Balrogs, they were described as lesser spirits while Sauron was described as a greater spirit amongst those that were corrupted by Melkor.
Sauron's rise to power in the Second Age is portrayed in the Amazon prequel series The Lord of the Rings: The Rings of Power. He first appears disguised as the non-canonical human character Halbrand, and then in the second season as Annatar (a canonical alias of Sauron), both played by Charlie Vickers.
Frodo, Sam, and Gimli eventually died, even there. They are lands of peace, which Frodo needed in order to properly heal. What their days there looked like, it is unclear. But they did not gain the immortality of the Elves or the Valar.
Aunt Google would tell you that his very first (and original ) name as a Maia is Olorin, The elves called him Mithrandir (Grey Pilgrim), Men named him Gandalf (the Grey, later the White), Dwarves knew him also under Tharkun, and in the deep South of ME he was also known as Incanus.
The Ent who figures most prominently in the book is Treebeard, who is called the oldest creature in Middle-earth.
Gandalf the White had more power but was still in a frail human shell. Dumbledore could easily kill Gandalf the grey or white, but death isn't permanent for Maiar. Dumbledore would stand no chance against Gandalf in his true Maiar form.
If Gandalf had stayed dead after his sacrifice in The Fellowship of the Ring, then his demise would be the saddest in the trilogy, but since he came back, the saddest single death scene of all three movies goes to Boromir's.
Gandalf essentially died in his fight with the Balrog. When this happened, God pulled him out of this world and sent him back after a time. From Gandalf's perspective, this was eons of time. He returned with as the same person, but with only distant memories of what was going on.
His task was to do the bidding of his masters and so when he proved unfaithful in doing that task his masters stripped him of his robes and gave them to one who would do their bidding. Gandalf is now the White, Saruman as he should have been.
Sauron was originally a Maia of Aulë the Smith; his name then was Mairon, meaning "the admirable." He learned much from Aulë in the ways of forging and crafting, becoming a great craftsman, and mighty in the lore of Aulë's people.
Gandalf is not permitted to use his full power during the 3rd Age (some exception apply). He has been sent to guide humans to the 4th age, the age of mortals. He can perform minor magic as needed, but he cannot "bust out."
Tolkien's Legolas is extremely introverted. He just doesn't have much to say directly to anyone, perhaps because he's thousands of years old. His odd relationship with Gimli draws him out in a way the hobbits never do, and that's mostly after Frodo and Sam leave the Fellowship.
Instead, we have to consider that Sauron, the original owner, is not human, but has a quasi-divine status. Therefore ownership of the Ring is subject to Divine Law. With this precedent in mind, many of the ambiguities clear up nicely. After numerous transfers by violence and trickery, Frodo is the true owner.
The Posttraumatic Stress Disorder of Frodo Baggins
J.R.R. Tolkien in The Lord of the Rings accurately portrayed the signs and symptoms of what is currently labeled Post Traumatic Stress Disorder. Frodo's condition logically follows his experiences of less than a year in the War of the Ring.
The clearest same-sex relationship in the novel, in the eyes of scholars, is that of the ringbearer Frodo Baggins and his servant, originally his gardener, Sam. Tolkien described their relationship as like that of an officer in the British Army and his military servant or batman.