What's the difference between よろしくねがいする and よろしくおねがいします?


よろしくねがいする as opposed to よろしくおねがいします.

This is, at this point, probably outside of my level.

I would like to know if よろしくねがいする:

  * is used and correct, and 
  * has the same nuance and context.

While not completely memorized and understood, I noted that the kenjougo [the
お- and the -します stem] is used to make it more formal/polite. But how that
affects the overall use, I'm not sure.




> (1) よろしくお願{ねが}いします  
>  (2) よろしく願｛ねが｝いする
>
> (3) よろしくお願｛ねが｝いする

(1) is an ordinary expression used when asking something to others. It is
common sense to use polite expressions when asking for something to others. It
seems that polite words/expressions such as "お願い" for "願い" and "します" for "する"
are used in (1).  
"します" for "する" is certainly a polite form, but concerning "お願い", which I'll
explain later, can not be said so in (1).  
We don't use (2), but use (3).  
(3) is used when the person who is higher in position or status like the
company's superior asking something to the person like his subordinate.

As for 願いする in (2), it is not a Japanese expression. As you know する sometimes
makes a noun a verb like お願いする（お願い+する）, but 願い cannot become a verb by being
added する. Therefore the expression with (2) is not used or is not a Japanese
sentence because 願いする doesn't make sense.

# EDIT

I'll provide more information on the difference between 願い and お願.  
Regarding the basic form of a sentence using "願い" is like "願いが
かなう/実現｛じつげん｝する/成就｛じょうじゅ｝する _wishes come true_ ". Furthermore, when the basic
form is modified, it'll become like "「私」の「日本語が上手になりたいという」願いが 実現する/成就する/かなう _My
wish that I want to be good at Japanese language comes true_ ".  
On the other hand, regarding "お願い", though "よろしくお願いします" is often used, it is
not a complete sentence. "「Aさん」に「Ｂ」をよろしくお願いします" is a complete sentence
composition. In general, Aさん is often "you", so omitting "you", there are many
cases that we use "Ｂをよろしくお願いします". Furthermore, as B is often clear in the
conversation as a context, "Bを" is omitted and the expression with
"よろしくお願いします" is commonly used.  
Therefore, simply the phrase with "よろしくお願いします" means "「私たちがいままで話してきたこと _what
we have been talking about_ 」 を 「あなた」によろしくお願いします".

You can use 願い and お願い at the same time to create the following sentence.

> 私は神様{かみさま}に私の **願い** が実現｛じつげん｝するように **お願いする** 。

However, it is incorrect to say "私は神様に私の **お願い** が実現するように **願いする** "




よろしくお[願]{ねが}いします is a very common phrase, and its お願いします part consists of:

> Continuative/Pre-masu form 「[願]{ねが}い」+ Humble expression (謙譲語)「お～～する」

します is the polite form of する.

願い is the continuative/pre-masu form (連用形), or the noun form, of the verb 願う.
And here it's used in the sense of:

> ねがう【願う】〘動五〙  
>  ➌他人に対して、こうしてほしいと頼む。「寄付を **願う** 」「協力を **願います** 」  
>  (表現)...「願い上げます」「 **お願いします** 」「お願い致します」「お願い申し上げます」  
>  （明鏡国語辞典）

* * *

A few examples of the humble form 「お・ご～～する・します」:

> 「 **お** [聞]{き}き **する** 」「 **お** [送]{おく}り **する** 」「 **お** [知]{し}らせ **する** 」 (
> _generally_ , お is used with native Japanese words)  
>  「 **ご** [案内]{あんない} **する** 」「 **ご** [報告]{ほうこく} **する** 」「 **ご** [提案]{ていあん}
> **する** 」 ( _generally_ , ご is used with Sino compounds)

For more on regular honorific and humble forms, [this
thread](https://japanese.stackexchange.com/a/54417/9831) might be of some
help.

* * *

「ねがいする」「ねがいします」 would be incorrect because **ねがい is not a する-verb (サ変名詞)**.

If you want to just convey "I ask a favor of you" without using the 「お～する」
form, you could instead use [頼]{たの}む, as in 「(よろしく)[頼]{たの}みます。」 or just
「(よろしく)[頼]{たの}む。」, but not 「[願]{ねが}いします。」.

