Is there a possibility SNS topic subscription can filter messages based on custom message header ? And Does SNS supports message grouping ?

Hello, good question

For the first part, may be filter policies can be used (Note: A filter policy can have a maximum of 5 attribute names and Amazon SNS ignores message attributes with the Binary data type.) https://docs.aws.amazon.com/sns/latest/dg/example-filter-policies.html

The following is for the second part of the question SNS seems to support publishing batches of up to 10 messages in a single API request https://aws.amazon.com/about-aws/whats-new/2021/11/amazon-sns-supports-publishing-batches-messages-single-api-request/

Blog post: https://aws.amazon.com/blogs/compute/publishing-messages-in-batch-to-amazon-sns-topics/