Turn on Anonymous access

I have been trying to turn on this anonymous access
gone through many thread and list on how to do it. none of them seems working

I have 7.14.1
basic license and user login is enable with just some role/spaces.

I created admin user with full access just for testing.

added following in to kibana.yml

xpack.security.authc.providers:
  basic.basic1:
    order: 0
  anonymous.anonymous1:
    order: 1
    credentials:
      username: "anonymous_service_account"
      password: "anonymous_service_account_password"

added following in to Elasticsearch.yml

xpack.security.authc:
  anonymous:
    username: anonymous_user
    roles: admin
    authz_exception: true

but it does not work. I can't login as anonymous user period.

Login prompt appears like this

Then errors when I click on Continue as guest

Error: [security_exception: [security_exception] Reason: unable to authenticate user [anonymous_service_account] for REST request [/_security/_authenticate]]: unable to authenticate user [anonymous_service_account] for REST request [/_security/_authenticate]
    at login_form_LoginForm.loginWithSelector (http://houelkdev01:5601/42747/bundles/plugin/security/8.0.0/security.chunk.5.js:8:22273)

On some other thread I saw following and added that in kibana as well but no luck

Created user anonymous/anonymous and assign role=admin(which I have created for test)
used this
https://github.com/elastic/kibana/pull/79985

xpack.security.authc.providers:
  basic.basic1:
    order: 0
    description: "Log in as an Employee"
  anonymous.anonymous1:
    order: 1
    description: "Continue as guest"
    icon: "globe"
    credentials:
      username: "anonymous"
      password: "anonymous"

What do I have to do in order to turn this on?
I want anonymous user which will be used via iframe just to display one or more dashboard.

Did you create the anonymous_service_account user in Elasticsearch?
If you configure Kibana's anonymous access in this way, it needs to use a real username and password that is valid in Elasticsearch.

yes created that user but got error

Anyone has any more clue?