Hello,

Try to use the below article for help with Embed blocks:

https://www.appsloveworld.com/wordpresscode/4/how-to-remove-the-core-embed-blocks-in-wordpress-5-6?expand_article=1

As for the CSS issue, the page is cached and to see the changes you need to clear the cache and then the changes will be uploaded. The cache plugins have such work so it’s not an issue.

https://wp-rocket.me/wordpress-cache/

Kind Regards