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 backyard with a chair covered in snow'. Reverse all words of length '4' in the given sentence.
Example Output: a backyard htiw a chair covered in wons

Example Input: Sentence: 'there are many animals standing on the top of this mountain'. Reverse all words of length '4' in the given sentence.
Example Output: there are ynam animals standing on the top of siht mountain

Example Input: Sentence: 'a couple of boats are tied to posts in the water'. Reverse all words of length '4' in the given sentence.
Example Output:
a couple of boats are deit to posts in the water