Can I create more than one environment in a. free app plan?
Do I need to subscribe to a plan if I need to have more than one environment (e.g. Test and Production), or I can do it with a free app too?
Yes, if you want extra environment you need to subscribe to a plan. The free app is just the one environment.
When using the free app you only get a single sandbox. It will also fall asleep when it is not used