This is a variation of Abarcadraba.

Consider all possible valid English words having at least 4 letters and at most 13 letters that satisfies the following conditions:

• Each word begins and ends with the same letter, and:
• Reversing the letters we obtain another valid English word, and:
• None of the words can be palindromes, and:
• None of the words can be plurals, proper nouns or abbreviations, and:
• None of the words can be hyphenated like A-bomb, X-ray etc.

What are the respective shortest word and the longest word that satisfy all the given conditions? Does there exist any valid English word having more than 13 letters that satisfies all the conditions?