what is the profession of the one who wrote the last version of it?
He was an English Anglican clergyman and abolitionist, also having been Captain of slave ships and investor of trade
John Newton
John Newton (; – 21 December 1807) was an English Anglican clergyman and abolitionist, also having been Captain of slave ships and investor of trade. 
who wrote the last verse of amazing grace John Newton is it a poem? It is a Christian hymn who sang in the recorded version of it? Edwin Othello Excell is one of them was there any revival happened because of this hymn? Yes, Dwight Moody and Ira Sankey heralded another religious revival giving the song international exposure
wiki:7693219
John Newton [SEP] Introduction
John Newton (; – 21 December 1807) was an English Anglican clergyman and abolitionist, also having been Captain of slave ships and investor of trade. He served as a sailor in the Royal Navy for a period after forced recruitment. Newton went to sea at a young age and worked on slave ships in the slave trade for several years. In 1745, he himself became a slave of Princess Peye, a woman of the Sherbro people. He was rescued, returned to sea and the trade, becoming Captain of several slave ships. Some years after experiencing a conversion to Christianity Newton later renounced his trade and became a prominent supporter of abolitionism.