Short answers, pulled from the story.
DJ Hollywood was the first person recognized as a rapper in the modern sense. He began rhyming syncopated to the beat of existing records in 1975. He adapted lyrics from Isaac Hayes and rhymed them to the breakdown of Love Is the Message.
The golden age of hip-hop spanned from the mid-1980s to the early 1990s. This period featured a critical mass of mic prodigies creating complex wordplay and lyrical kung-fu. The era is considered to have ended around 1993 or 1994.
The current record for fastest rapper is held by Spanish rapper Domingo Edjang Moreno. He is known by his alias Chojin and rapped 921 syllables in one minute on the 23rd of December 2008.
Freestyle rap has evolved since the late 2000s to become the most commonly referred to style when the term is used. Its primary focus has morphed from making up a rap on the spot to reciting memorized or written lyrics over an undisclosed beat. The more difficult and respected style involves completely improvising the session's rapped lyrics.
Rapper Drake popularized the acronym YOLO in 2012 when he featured it in his own song The Motto. The term became a trending hashtag on Twitter and was printed on t-shirts that same year.
The Migos Flow is a new rap flow heavily dependent on triplets. An American hip-hop collective from Atlanta named Migos popularized this flow in 2014. The term is commonly referred to as the Migos Flow within the hip-hop community.