Questions & Answers about Перед прогулкой я надеваю на собаку ошейник и беру поводок.
Because the preposition перед normally requires the instrumental case when it means before.
So:
- прогулка = walk
- перед прогулкой = before the walk
For a feminine noun ending in -а, the instrumental singular often ends in -ой:
- прогулка → прогулкой
So this is a case-governed form, not the dictionary form.
Here перед means before, as in before going for a walk.
But перед and до are not always interchangeable:
- перед прогулкой = before the walk, often right before it
- до прогулки = before the walk, but more abstractly or as a time limit
In this sentence, перед прогулкой sounds very natural for a routine that happens immediately before the walk.