Instagram giveaways are great for attracting attention, especially when the prize is truly compelling. But I think a lot depends on the terms and conditions.
The easier the participation and the clearer the rules, the more people actually participate, rather than just scrolling past the post.
When running contests and giveaways on Instagram, one of the main challenges is verifying that the terms and conditions have been met, especially if a recent following of the organizers or sponsors was a mandatory requirement. If you need to quickly check participants and see latest followers instagram you can use this service. The app itself has long shuffled the follower list, making it nearly impossible to manually find a new participant.