1) What is the difference between Sling content distribution and Simple Replication. 2) How can we perform reverse replication from publisher to author (not sling content distribution)?

Hi @shikhasoni1, SCD (Sling Content Distribution) is an API based content distribution to manage how the content is sent and received between different sling instances. There are three different types of distribution in SCD which are Forward, Reverse and Sync.
While most of the use cases can be done using simple replication/reverse replication instead of SCD. Below are a few key advantages of using SCD over Agent Replication:

1. In SCD, the distribution is done from one or more source instances to one or more target instances. In Agent Replication, we need to setup multiple replication agents.
2. In SCD, sending and receiving ends, both needs to be configured. In Agent Replication, for replication, only the author agent needs to be configured.
3. In SCD, sync distribution helps sync content across many publishers which is controlled by author instance. This type of use case where we need to sync data across multiple publishers may not be easily achieved using the Agent Replication.

As defined in #3, this is the major benefit of using SCD over Agent Replication.

To set up reverse replication (publisher to author) please refer this guide: https://www.cqtutorial.com/courses/cq-admin/cq-admin-lessons/configure-cq-replication/cq-reverse-replication

For more details on SCD, please refer these links:
https://sling.apache.org/documentation/bundles/content-distribution.html
https://www.albinsblog.com/2020/08/sling-content-distribution-in-aem-sync-content-between-publish-instances.html

- Jineet