Did Sauron know Gandalf had a ring?

No. Sauron never knows where the three are hidden. If he did, he would attack and take them, since only Sauron could get past their power if used to protect a land like Rivendell or Lorien.

Did Gandalf know Sauron was back?

5 years later in TA 2850, Gandalf once again returned to Dol Guldur and found Thráin, dying. Gandalf then confirmed that Sauron was indeed the master of Dol Guldur. Gandalf returned to the White Council and urged an attack on Dol Guldur, but was overruled by Saruman.

Was Sauron the same as Gandalf?

Sauron was stronger than Gandalf in the Lord of the Rings, but it has to be said that there were a few different shapes of both characters. Sauron was stronger than Gandalf the Grey, but probably not stronger than Gandalf the White. Also, there are their true Istari forms that should be compared.

Did Sauron know the ring could be destroyed?

Yes, Sauron knew exactly what and where The Ring could be destroyed. However it never occurred to him that anyone would actually attempt to destroy it, because The Ring was too powerful and precious. This was actually confirmed (to his mind) when Aragon wrested control of the palantir away from him.

Who did Sauron think had the ring?

It was hoped that Sauron would think Aragorn had the Ring and was now trying to use it to overthrow Mordor. As the journey progressed, Aragorn was credited openly as “the King Elessar” by their heralds to challenge Sauron. Aragorn had around 7,000 soldiers of Gondor and Rohan, some 6,000 foot and 1,000 horse.

Why does Gandalf tell Frodo not to put on the Ring?

Gandalf warns Frodo that he is already falling under the Ring’s power. Frodo asks Gandalf to take the Ring, but the wizard refuses vehemently. With the Ring, Gandalf says, he would become too powerful, and he would inevitably be corrupted like Sauron himself.

What did Sauron think when the Ring was destroyed?

Sauron believed he was strong enough to take shape again without the Ring but he believed that the Ring had been destroyed. After Sauron learned about the Ring from Gollum his knowledge of the facts changed. Once Gandalf confirmed that Bilbo’s ring was indeed the One Ring his knowledge of the facts changed as well.