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 couple walking in the rain using and umbrella'. Reverse all words of length '6' in the given sentence.
Example Output: a elpuoc walking in the rain using and umbrella

Example Input: Sentence: 'a blue sign sitting on the side of a road next to a tree'. Reverse all words of length '1' in the given sentence.
Example Output: a blue sign sitting on the side of a road next to a tree

Example Input: Sentence: 'a boy sitting down on his skateboard holding his hands'. Reverse all words of length '4' in the given sentence.
Example Output:
a boy sitting nwod on his skateboard holding his hands