In this task, you need to reverse all words of a given length in the sentence. The number of letters in a word determine its length. For example, the length of the word "apple" is 5.

Example Input: Sentence: 'a dog lays next to a bag on a couch'. Reverse all words of length '4' in the given sentence.
Example Output: a dog syal txen to a bag on a couch

Example Input: Sentence: 'a bird sitting in a tree next to a citrus fruit'. Reverse all words of length '6' in the given sentence.
Example Output: a bird sitting in a tree next to a surtic fruit

Example Input: Sentence: 'a bicycle is parked near a park bench'. Reverse all words of length '6' in the given sentence.
Example Output:
a bicycle is dekrap near a park bench