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 toilet and a roll of toilet paper'. Reverse all words of length '2' in the given sentence.
Example Output: a toilet and a roll fo toilet paper

Example Input: Sentence: 'a black do running on sand with all four feet in the air'. Reverse all words of length '4' in the given sentence.
Example Output:
a black do running on dnas htiw all ruof teef in the air