Correct Syntax for Robot.txt File? - wordpress

Question

What's below is in my Robot.txt file.
If I want a particular Search engine to have access to the site, but not a few key areas, such as the admin section, the wp-content area, and a folder that is non-existent, is the syntax that I have below correct for google, msn, bing, yahoo, duckduckbot, but to disallow everyone else ?
User-agent: Googlebot
Allow: *
Disallow: /wp-admin/*
Disallow: /wp-content/*
Disallow: /docs/*
User-agent: MSNBot
Allow: *
Disallow: /wp-admin/*
Disallow: /wp-content/*
Disallow: /docs/*
User-agent: Bingbot
Allow: *
Disallow: /wp-admin/*
Disallow: /wp-content/*
Disallow: /docs/*
User-agent: Slurp
Allow: *
Disallow: /wp-admin/*
Disallow: /wp-content/*
Disallow: /docs/*
User-agent: DuckDuckBot
Allow: *
Disallow: /wp-admin/*
Disallow: /wp-content/*
Disallow: /docs/*
User-agent: Google (+https://developers.google.com/+/web/snippet/)
Allow: *
Disallow: /wp-admin/*
Disallow: /wp-content/*
Disallow: /docs/*
User-agent: Googlebot-Image/1.0
Allow: *
Disallow: /wp-admin/*
Disallow: /wp-content/*
Disallow: /docs/*
User-agent: Googlebot-Video/1.0
Allow: *
Disallow: /wp-admin/*
Disallow: /wp-content/*
Disallow: /docs/*
User-agent: SAMSUNG-SGH-E250/1.0 Profile/MIDP-2.0 Configuration/CLDC-1.1 UP.Browser/6.2.3.3.c.1.101 (GUI) MMP/2.0 (compatible; Googlebot-Mobile/2.1; +http://www.google.com/bot.html)
Allow: *
Disallow: /wp-admin/*
Disallow: /wp-content/*
Disallow: /docs/*
User-agent: Mozilla/5.0 (Linux; Android 6.0.1; Nexus 5X Build/MMB29P) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.96 Mobile Safari/537.36 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)
Allow: *
Disallow: /wp-admin/*
Disallow: /wp-content/*
Disallow: /docs/*
User-agent: *
Disallow: *

Answer 1

Syntax is correct, but approach is wrong.
1. Never block your content
Google (and many other search engines) fully renders your page. If you block access to images, Google drops down your position is search results, just for a case. Googlebot cannot understand if your page is full of broken links to images, or not.
This is a quote from Maile Ohye, Google Developer Programs Tech Lead:
“We recommend making sure Googlebot can access any embedded resource that meaningfully contributes to your site’s visible content or its layout”
2. Do not block /wp-admin/admin-ajax.php
When you block access to /wp-admin/ entirely, no ajax content is available for robots. That is why standard robots.txt generated by WordPress on the fly is as follows:
User-agent: *
Disallow: /wp-admin/
Allow: /wp-admin/admin-ajax.php
3. Do not block other bots
List of search bots are wider than shown in your question, and grows occasionally. In your list, for example, Googlebot-Mobile does not present. The last statement in your file blocks access to this bot with evident results for mobile search.
It is better not to invent a bicycle, but use standard WordPress robots.txt settings shown above or even wider settings by Yoast SEO plugin (1+ million installs).