use this copyscape.com

Yes using double quotes ("") and paste you one line content into Google's search box. If it shows some result that are appears in bold as in the google snippet.
It is one of the way to check whether your content unique or not.
I have found here some tools which may be useful for you. But i haven't tried all the tools.
I am familiar with Copyscape and Small SEO tool .
Here is the tools. 5 Best Free Copyscape Alternatives to Catch content thieves - T.Entice

I always use copyscape myself, and really do think it's the best. You could try doing it the Google way with quotes, but that won't check the entire article really.. Your best bet is copyscape!

try these sites Siteliner - Find Duplicate Content on your site, duplichecker.com, copyscape.com or just copy the content and put it in google

That depends on what you mean by "unique". If you go by the useless definition of "no-one has used these words in this order" then yes, it's an unique article.

However, almost nobody makes exact match searches to find something. Google is able to understand contexts and synonyms. If your article has an unique order of words that doesn't mean that Google sees it as unique, or that you'll rank.