As @Ormus was saying, the Epic refund policy should give you plenty of time to check whether the game will run:
What types of products can I return for a refund?
Any game you purchase through the Epic Games store is eligible for a refund. Epic cannot provide refunds for purchases made outside of the Epic Games store.
If you receive a refund for a game, you will also receive a refund for all in-app and downloadable content purchases you made through the Epic Games store for that game, so long as that content has not been consumed, modified, or transferred.
When are products eligible for a refund?
All games are eligible for refund within 14 days of purchase for any reason. However, you must have not played the game for more than 2 hours.
You will not be eligible for refunds for games from which you have been banned or for which you have otherwise violated the terms of service. In addition, you may not be eligible for refunds if Epic determines that you are abusing the refund policy.