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 small white dog with a hat on his rear end'. Reverse all words of length '3' in the given sentence.
Example Output: a small white god with a tah on sih rear dne

Example Input: Sentence: 'this cat is sitting on a porch near a tire'. Reverse all words of length '7' in the given sentence.
Example Output: this cat is gnittis on a porch near a tire

Example Input: Sentence: 'a pair of boats are beside each other in the water'. Reverse all words of length '6' in the given sentence.
Example Output:
a pair of boats are ediseb each other in the water