Does the free tier require a credit card or credits to be added to the account?

If I am planning to stay on the free tier, do I need to add a credit card or credits to try out fly.io? I read the pricing page, was impressed with the free offering and decided to try it out. I installed flyctl and created an account to run a python script but it seems to be throwing an error.
Error We need your payment information to continue! Add a credit card or buy credit: https://fly.io/dashboard/personal/billing

Also, if a credit card is required, can I add a hard limit (like $5/month), after which my apps are taken offline in case they reach the $5 spending limit?

As far as I’m aware you do still need to provide a credit card (I assume partly to verify you are a real person/company, and partly to prevent any abuse with bots doing crypto-mining etc). But it won’t be billed if you stay within the free tier’s allowance.

For example if you only create (at most) 3 vms of the smallest type (and don’t enable auto-scaling) you could not exceed the free tier’s allowance of 3 vms. Similarly, don’t allocate more than 3 GB of storage (I believe the free limit is 3 GB).

As @greg said, the card is required, however, you can just instead purchase credits, unfortunately there is no way to set a hard limit, beyond buying credits.