IHG Accelerate is a popular stay challenge program of IHG that is renewed every 4 months. The challenge offered depends on a lot of factors including your stay history, locations etc. You might end with a lucrative challenge or something that's too difficult to achieve (like stay in 5 countries) or sometimes just not worth it. However, most people tend to get good offers.
You first need to register for the offer, find your custom target offers and earn points as you complete each challenge. It's a great way to earn bonus points if your upcoming stays can fit in the pattern.
You must register for the promotion by 18 October 2019.
Here's a sample IHG Accelerate challenge.