I am trying to list all the spaces, dashboards and watchers present on the entire elasticsearch cluster

Elastic Stack Kibana
1

I am using the below apis to get them

GET /api/spaces/space

POST /api/saved_objects/_bulk_get

All the above are giving 400, are they deprecated in v8.13.4 ?

2

The APIs you've linked to are Kibana APIs, so I've moved this to the Kibana forum.

Can you provide a minimal example (e.g. using curl) of what you're trying to do?

3

Where are you running those requests?

Those are Kibana APIs, so you need to make the request to Kibana, not Elasticsearch.

If you are running them on Kibana Dev Tools you need to prefix the endpoints with kbn:

For example:

GET kbn:/api/spaces/space