What are the benefits or impacts if we upgrade the manifest.json file's version in UI5?
In my manifest.json file currently "_version": "1.1.0" is maintained.
What will be the pros and cons if we change the version to "_version": "1.21.0"?
How will the overall application be affected?
The "_version" in manifest is the version of the schema the manifest file complies with. For using newer features in UI5, a newer manifest schema version might be required. On the other hand, each UI5 version does only work up to a certain manifest schema version as can be seen from the manifest.json documentation.
The version can be used for schema validation of the manifest file.
On the runtime side, there seems to be currently only one changed behavior based on the vesion of the manifest quite some time ago (since UI5 1.52, schema version 1.9.0).