Yes, this is achievable. Follow these steps to set it up:
1. Navigate to your survey and open the Edit section.
2. Go to Finish Options and select Rewards from the dropdown menu.
3. Set the Qualifying Criteria to First N number of completes.
Screenshot: https://prnt.sc/JNblhHmGGOQt
4. Specify the number of winners as 50.
Screenshot: https://prnt.sc/d80t6cP7OzQF
This setup will allow you to reward the first 50 respondents who complete the survey.