Definition: 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.
Input: Sentence: 'many cars drive down a busy street and people walk on the sidewalks'. Reverse all words of length '4' in the given sentence.

ynam srac drive nwod a ysub street and people klaw on the sidewalks