Where can I find all release note from version to version?

Elastic Stack Elasticsearch
1

Hello all,

My ELK stack is currently 6.5.4,
I would like to see the changes from 6.5.4 all the way to 7.4.0
Where can I find the full details of the updates? I would like to do the updates after reading the changes.
Thanks.

2

See https://www.elastic.co/guide/en/elasticsearch/reference/7.4/es-release-notes.html and https://www.elastic.co/guide/en/elasticsearch/reference/6.8/es-release-notes.html

You also may want to take a look at the breaking changes at https://www.elastic.co/guide/en/elasticsearch/reference/7.4/breaking-changes.html - and here down to 7.0, as most of them happen in major version upgrades.