3 – I also would like the image to stay in the actual size and not miniature.

Set your preferences for both 1 and 3 in the forum admin > Options > Content panel.

1 and 3 solved.

Can you help me now in question 2?
It will be because I have the plugin “TinyMCE Advanced” installed on WP? There is another plugin that does not cause conflict?

well, I can assure you that we make no special checks for displaying the editor to users or admins… so that means you have something else on your site, that is affecting tinymce…

since this is just the wp editor, I suspect you have a theme or plugin that is adding additional buttons to the editor in the admin for writing posts… unfortunately, many of those themes and plugins make the bad assumption that the wp editor only shows in the admin… very wrong and not how the wp devs designed it…

do you get extra tinymce buttons in the admin wp editor?

if we can identify if the theme or plugin is adding the buttons, we can help correct it if they are doing wrong…

I uninstalled Plugin for wordpress “TinyMCE Advanced”. And the problem was corrected.
I wonder if there’s a plugin for wordpress that does not cause this problem.
I must have well over buttons for formatting text editor for blog posts.

We figured it would be something like that.

Try taking a look in the plugins main code file – usually has the same name in the root folder of the plugin. Somewhere in there you will almost certainly find a line of code that starts with:

add_action('init',

try changing that to:

add_action('admin_init',

and see if that resolves it…