How was Voldemort planning to return into power (meaning having a body) after the eventuality that he was defeated but one or more Horcruxes survived?
Was any one of the more trusted Death Eaters aware of the existence of the horcruxes and able to help him?
If not, the Horcruxes (except for the snake) could not move and can interact only with people who get close. Was the plan just to wait for the right occasion, as in the time when Voldemort was destroyed by the rebounding curse?
It's worth remembering that, as far as we know, Voldemort was only the second person in history to make a Horcrux. It wasn't widely known what happens to a wizard who dies after creating a Horcrux. Even Voldemort probably didn't know at the time. All he knew is what he learned from Horace Slughorn.
A Horcrux is the word used for an object in which a person has concealed part of their soul.”
“I don’t quite understand how that works, though, sir,” said Riddle.
His voice was carefully controlled, but Harry could sense his excitement.
“Well, you split your soul, you see,” said Slughorn, “and hide part of it in an object outside the body. Then, even if one’s body is attacked or destroyed, one cannot die, for part of the soul remains earthbound and undamaged. But of course, existence in such a form...few would want it, Tom, very few. Death would be preferable."
(Half-Blood Prince, Chapter 23, Horcruxes).
It seems that Voldemort didn't know exactly what would happen should he ever have to rely on his Horcruxes until his downfall at Godric's Hollow.
“I miscalculated, my friends, I admit it. My curse was deflected by the woman’s foolish sacrifice, and it rebounded upon myself. Aaah...pain beyond pain, my friends; nothing could have prepared me for it. I was ripped from my body, I was less than spirit, less than the meanest ghost...but still, I was alive. What I was, even I do not know...I, who have gone further than anybody along the path that leads to immortality. You know my goal - to conquer death. And now, I was tested, and it appeared that one or more of my experiments had worked...for I had not been killed, though the curse should have done it. Nevertheless, I was as powerless as the weakest creature alive, and without the means to help myself...for I had no body, and every spell that might have helped me required the use of a wand..."
(Goblet of Fire, Chapter 33, The Death Eaters).
Voldemort is quite open about his ignorance of how Horcruxes truly work and what state he was in when he was depending on them. He wasn't prepared for the circumstances in which he'd be a ghost-spirit because there was no real precedent. He was pushing the boundaries of experimental magic. Nobody could really have predicted what would have happened to him.
Additionally, of course, Voldemort never expected to have to rely on his Horcruxes. They fed his ego by reassuring him that he was immortal (and therefore superior to every other wizard). They were a failsafe. But Voldemort was confident enough in his own abilities that he never expected to have to rely on them. He never expected to die. As such, he never prepared for the circumstance he found himself in. He subsequently hoped that one of his Death Eaters would come looking for him but he didn't prep them for that eventuality in his earlier life because he never expected to die in the first place.
It was Voldemort's arrogance that has been reiterated throughout the series. He always believed he knows best. He was proud that he went "further on the path that led to immortality" than any other, not realizing it led to his soul becoming unstable which allowed it to be ripped apart and latch onto Harry.
In his arrogance he didn't feel that he needed a fullproof plan. The horcruxes were just his fancy, because he believed he was the most powerful wizard. When he fell he was surprised that none of his loyal Death Eaters came to find him and offer him support. He was able to regain his body with the help of a very incapable wizard who was also on the run. If he had the support of someone such as Lucius Malfoy, surely he'd be back VERY soon.
In his arrogance, he took the loyalty of his followers for granted, didn't realize his own blind spots and didn't anticipate Dumbledore's knack for finding information and making educated "guesses".
To answer your second question: No. No one but Voldemort knew the existence of his horcruxes. He trusted no one. Lucius and Bellatrix were just honoured enough with keeping safe the pieces of his souls, without knowing what they were. Dumbledore comments how Lucius tried to get rid of "an incriminating piece of evidence" by plotting for his downfall and ruining the reputation of Arthur Weasley.
