Who is the Prophet Daniel, and is it true that the Companions found his body during the era of Umar ibn al-Khattab, whereupon they reburied it?

Daniel is a prophet of the Children of Israel from the time of Nebuchadnezzar, and he prophesied about Muhammad (peace and blessings be upon him) and about the Messiah.

When Tustar was conquered, the Muslims found his body. Umar then ordered that it be buried secretly in an unknown place, fearing that he might become an object of fitna (strife/temptation).

He had a ring on his hand, engraved with two lions licking him. When asked about this engraving, they said: The king wanted to kill Daniel at his birth, so they threw him into a lion's den. The two lions then spent the night licking him, and they did him no harm. So, Daniel engraved that on his ring in gratitude to Allah.

It was said that he was 300 years old when he died, but Ibn Kathir considered this unlikely, because there was no prophet between Jesus and Muhammad. He suggested that Daniel died much earlier than that, or that he was another righteous man, and that the earth does not consume the bodies of prophets.