No, due to the rule of two, Sidious would be unable to take 2 apprentices at one time. The rule of two stated only two Sith could be at the top of the Empire (one Sith lord and his apprentice = Sidious and Maul). Dooku left Sidious's apprenticeship before he took on Maul.
No, but he meets him in the Son of Dathomir comic. This comic was actually an adaptation of an unfinished TCW arc, so it was very close to coming to fruition.
But there is a version of this where Dooku only knows right before the Battle of Coruscant in Revenge of the Sith, and prior to that, like Maul and everyone else, he was also unaware of exactly how Darth Sidious was controlling the Senate.
A deadly, agile Sith Lord trained by the evil Darth Sidious, Darth Maul was a formidable warrior and scheming mastermind. He wielded an intimidating double-bladed lightsaber and fought with a menacing ferocity.
Darth Maul
Even though they were both trained by Palpatine, Dooku and his predecessor, Maul have been enemies every since his mind was restored by Mother Talzin. This is because the two hated each other. Dooku despises Maul for being a threat to him and Maul hated Dooku for being his replacement.
Another contender for the weakest Sith could be Count Dooku, or has he's also known Darth Tyranus. Dooku was a cunning and talented Sith Lord, known for his swift skills with a lightsaber and his ability to manipulate populations.
In one of the canon comics Sidious outright implied that Maul was pretty much head and shoulders above Dooku when adressing the potential. While Dooku was a useful pawn for him, Maul in the other hand seems to be actually his first choice as a heir before Anakin was really part of the picture at least.
Later stripped of his black Nightbrother markings, Maul was left solely red-skinned. Agonizing Sith tattoos were applied personally by Darth Sidious in an attempt to cleanse Maul's mind as well as demonstrating Maul's complete dedication to the dark side.
Darth Maul died during a final battle with Obi-Wan in the Rebels TV series, and Palpatine couldn't have cared less. For him, finding and killing Maul for his failure simply wasn't worth the effort.
Darth Maul and Obi-Wan's long-standing rivalry started in Episode 1 and lasted all the way until Star Wars: Rebels. Throughout his lifetime, Maul seemed to hate Kenobi! Every time Maul says Kenobi.
Bottom line, Dooku never considered himself a Sith. And he wasn't; he was a man looking to change the galaxy in a way the Jedi were unwilling to try. And that is why he joined the Sith and became Darth Sidious' apprentice, Darth Tyrannus. When Dooku became Sidious's apprentice, he was already an elderly man.
The individual would pull their dark powers into themselves and adopt a mask of insignificance. This projected illusion would enable a Sith to hide in plain sight whenever they would go out in public.
If Maul knew, he would have tole Obi Wan or another Jedi during the Clone Wars. Dooku knew Palpatine was Sidious as he told Obi-Wan about him controlling the senate and referred to him as the dark lord. There's no real way of actually knowing if he knew ab palpatine.
Mission to Mathas. Padawan Windu was trained in the ways of the Force by Jedi Master Cyslin Myr. Following his early trials as a youngling, Windu attained the status of Padawan by becoming Jedi Master Cyslin Myr's apprentice.
His former colleagues in the Jedi Order saw Dooku as misguided but a man of principles, and refused to believe he could be an advocate of violence and war. They were wrong; Dooku had sworn allegiance to the Sith Lord Darth Sidious, taking the name Darth Tyranus.
Maul rivals Dooku in saber skills and is physically superior to the Count. Though DOoku is in better shape, is stronger, is faster, and more durable than most men his age (there are numerous sources of this just ask and I'll explain).
However, Maul's hatred of the Jedi was more personal. He was filled with anger when he realized that as a child, the Jedi had not come for him. Maul did not know if they found him unworthy or simply ignored him, and their neglect fueled his rage, counting the days until he could have his revenge.
DARK SIDE FRIDAY - Did you know Palpatine feared Qui-Gon Jinn? Palpatine was immensely powerful and he could see the future which made him very confident about pretty much anyone who stood against him. So why Qui-Gon Jinn?
Feeling abandoned by Palpatine, a.k.a. Darth Sidious, Maul could no longer bear the Sith mantle of Darth in accordance with the Rule of Two, since Palpatine had since taken on a new apprentice after Maul's apparent death on Naboo.
Regardless, Dooku's eyes weren't yellow because he wasn't motivated by anger. He was merely a practical dark side user, so he does not have the usual Sith eye color.
According to Star Wars Legends content, the first Sith was a former Jedi Master, Ajunta Pall, who became a so-called Dark Jedi, or “Fallen” Jedi. As the name implies, these Force-sensitives chose to practice the Dark Side, and rejected the Light Side of the Force.
Though one thing is for certain: Kylo Ren/Ben Solo does not have yellow eyes because he's not "corrupted" by the Dark Side. This isn't a bad answer, though it does go off on a tangent.
Sidious broke the Rule of Two at least twice: once by training Darth Maul while still under the tutelage of Darth Plagueis; and secondly, by taking on two apprentices at once, and in the form of two Jedi: Count Dooku, the former Padawan of the legendary Jedi Master Yoda, dubbed Darth Tyranus, and the Fosh Jedi Vergere.
Studying Jedi Archive records, Dooku based his new weapon design after the curved hilts that were standard during the heyday of Form II lightsaber combat. The curve allowed the hilt to fit better into his hand, allowing for superior finesse and precise blade control.
Revenge of the Sith (2005)
Anakin gives in to his hatred of Dooku and uses his anger to overpower him, severing both of Dooku's hands and leaving him helpless.