During the 16th Century, u and j were introduced as letters different from v and i, and w also became a distinct letter. See link for more.
R would be the 13th letter in the English alphabet after the letter E. E is the 5th letter and R is the 18th letter in standard alphabetical order. There are 26 letters total in the English alphabet.
The alphabet has 26 letters. The letter "D" comes after the letter "C".The English alphabet, in order:ABCDEFGHIJKLMNOPQRSTUVWXYZ
The alphabet has 26 letters. The letter "B" comes after the letter "A".The English alphabet, in order:ABCDEFGHIJKLMNOPQRSTUVWXYZ
The alphabet has 26 letters. The letter "I" comes after the letter "J".The English alphabet, in order:ABCDEFGHIJKLMNOPQRSTUVWXYZ
The alphabet has 26 letters. The letter "H" comes after the letter "I".The English alphabet, in order:ABCDEFGHIJKLMNOPQRSTUVWXYZ
The alphabet has 26 letters. The letter "C" comes after the letter "B".The English alphabet, in order:ABCDEFGHIJKLMNOPQRSTUVWXYZ
The alphabet has 26 letters. The letter "G" comes after the letter "F".The English alphabet, in order:ABCDEFGHIJKLMNOPQRSTUVWXYZ
The alphabet has 26 letters. The letter "R" comes after the letter "Q".The English alphabet, in order:ABCDEFGHIJKLMNOPQRSTUVWXYZ
The alphabet has 26 letters. The letter "T" comes after the letter "S".The English alphabet, in order:ABCDEFGHIJKLMNOPQRSTUVWXYZ
The alphabet has 26 letters. The letter "K" comes after the letter "J".The English alphabet, in order:ABCDEFGHIJKLMNOPQRSTUVWXYZ
The alphabet has 26 letters. The letter "N" comes after the letter "M".The English alphabet, in order:ABCDEFGHIJKLMNOPQRSTUVWXYZ
The alphabet has 26 letters. The letter "P" comes after the letter "O".The English alphabet, in order:ABCDEFGHIJKLMNOPQRSTUVWXYZ