I revoked permissions for public as you said. Then I connected to Object Explorer with an SQL login that owns a database, and in that database I tried to do SELECT TOP 1000 Rows, and indeed I got those errors.
Next, I did this in master:
CREATE ROLE regreaders CREATE USER MyUser ALTER ROLE regreaders ADD MEMBER MyUser GRANT EXECUTE ON [sys].[xp_instance_regread] TO regreaders
Then I reconnected in Object Explorer (so that the tokens are picked up correctly.) I was now successful in running the SELECT TOP 1000 Rows.
However, I would suggest that if you have been told to revoke permissions on xps for public, you should start to grant permissions to users by other means, but tell people that they will need to use SELECT statements. Else you are not obeying to the guidelines that your security people have given. Also, personally, I don't like adding users to the master database.
As for editing posts, there is a cogwheel in the upper-right corner of your post. There is a menu which includes an Edit alternative (if the post is yours). For Comments, you find Edit under "More" below the post.