and who amongst them was the founder of the group?
John Lennon formed a skiffle group in 1957 initially known as The Quarrymen which was later changed to The Beatals in 1960.
The Beatles
In March 1957, John Lennon, then aged sixteen, formed a skiffle group with several friends from Quarry Bank High School in Liverpool. They briefly called themselves the Blackjacks, before changing their name to the Quarrymen after discovering that another local group were already using the name. Fifteen-year-old Paul McCartney joined them as a rhythm guitarist shortly after he and Lennon met that July. In February 1958, McCartney invited his friend George Harrison to watch the band. The fifteen-year-old auditioned for Lennon, impressing him with his playing, but Lennon initially thought Harrison was too young for the band. After a month of Harrison's persistence, during a second meeting (arranged by McCartney), he performed the lead guitar part of the instrumental song "Raunchy" on the upper deck of a Liverpool bus, and they enlisted him as their lead guitarist.

By January 1959, Lennon's Quarry Bank friends had left the group, and he began his studies at the Liverpool College of Art. 
what is the song a day in the life about It is the concerning reality revealed by LSD to be largely in the eye of the beholder. who was it’s singer? The Beatles who were members of this band? John Lennon, Paul McCartney, George Harrison and Ringo Starr.
wiki:19676351
The Beatles [SEP] 1957–1963: Formation, Hamburg, and UK popularity
In March 1957, John Lennon, then aged sixteen, formed a skiffle group with several friends from Quarry Bank High School in Liverpool. They briefly called themselves the Blackjacks, before changing their name to the Quarrymen after discovering that another local group were already using the name. Fifteen-year-old Paul McCartney joined them as a rhythm guitarist shortly after he and Lennon met that July. In February 1958, McCartney invited his friend George Harrison to watch the band. The fifteen-year-old auditioned for Lennon, impressing him with his playing, but Lennon initially thought Harrison was too young for the band. After a month of Harrison's persistence, during a second meeting (arranged by McCartney), he performed the lead guitar part of the instrumental song "Raunchy" on the upper deck of a Liverpool bus, and they enlisted him as their lead guitarist.