Beow (whose name translates to "bee" in Old English), was famous "through the north," as a prince, and later a king, in a prized lineage. Beow was the son of Shield Sheafson a terrifying king, whom the narrative of Beowulf begins with (Beow was no relation to Beowulf, whose name translates to "bee-wolf," figuratively a bear). If Beow was as well known as his father, although it is not clear how he becomes so in the poem, he must have been as vicious a ruler and conqueror as his father. Twice in the epic, it is mentioned that Beow was sent forth by God, alluding to the origin of his fame as well. He ruled for many years following the death of his father, until "the great Halfdane" ruled as his heir. One of the Halfdane's sons was named Hrothgar, whose great hall is the subject of the first half of the poem. A major tenet of the epic poem is the establishment of lineage, and the anonymous poet provides a fine example of this in Beowulf.
I am not quite sure how you mean this. The original manuscript of Beowulf was contained in the religious monestary records of Henry VIII. Many of the monasteries records were destroyed during the upheaval between Henry VIII and the church. Sir Robert Bruce Cotton later owned the manuscript but had a terrible fire that almost ruined it.
Since Beowulf was a Geat, his story was probably written by the Geats. However, the exact author was unknown. In 1981 Professor Kenin Kiernan wrote a book about the poem which created a controversy that led to a reawakening of the value of the epic poem. Since then it has been made into movies, plays,and had many versions adapted from the Old English version.