C :: For Every Char Of Given Alphabet - Count How Many Times In The String

Be given a string of chars, where each single char belongs to the following alphabet: a..zA..Z0..9 (So, in the string there are only lowercases, uppercases and digits. No blank, no comma, ...).

For every char of the given alphabet, count how many times in the string

1----- the char is preceded by its predecessor in the alphabet (consider that the predecessor of 'a' is '9')
2----- the char is followed by its successor in the alphabet (consider that the successor of '9' is 'a')
3----- the char belong to a sequence of identical chars whose length is at least three (i.e.: in the string cc74uyrpfccc348fhsjcccc3848djccccc484jd for three times the character 'c' satisfies this condition)
4----- what is the longest substring of characters strictly rising (the following is greater (>) of the previous)
5----- what is the longest substring of successive characters (i.e.: fhkjshdfruytyzABCDEfglsj => 7)
6----- the frequencies of any char (if in the string the character 'g' occurs 12 times, its frequency is 12)