I got a mail that my "Your Amazon Web Services Free Tier expires soon" so as to delete any active resources. How can I do it for my DeepRacer service ?

The list of active resources takes time to be updated. Please refer to "Confirm that active resources are terminated" in the following document to check if there are any active resources remaining. https://repost.aws/knowledge-center/check-for-active-resources

1. Open AWS Resource Groups.
2. In the navigation pane, on the left side of the screen, choose Tag Editor.
3. For Regions, choose All regions.
4. For Resource types, choose All supported resource types.
5. Choose Search resources. If search results appear, then there are still active resources on the account.
   Note: Resource Groups search results don't show AWS Marketplace subscriptions. To manage subscriptions, see Managing your software.

If you are able to delete unnecessary services, there is no problem because the fee will no longer be incurred.

I have deleted all the resources following your guidelines. But still the Billing Management console shows my DeepRacer [usage quantity has increased]. Also S3 have been added [Proofs of screenshot have been shown in the question]

You must first understand the S3 fee structure. As noted in the following document, S3 also charges for APIs that display lists and the like. (Up to 2,000 times per month is free.) The reason for the invoice this time is because from the console you checked the S3 list and performed the deletion. Also, as you can see from the invoice, the number of API requests is included in the free usage tier and will not be incurred as payment this month. https://aws.amazon.com/s3/pricing/?nc1=h_ls
Also, once something is listed on that invoice, it is not updated until the end of the current month, so that list will not be updated until next month. If you can confirm that there are no resources at the URL I provided, ""Confirmation of active resource termination"", then you will not be charged for this month.