おんえがいします is wrong, it does not exist.
Remember that when you are learning japanese the first thing you have to learn correctly is Hiragana and then Katakana so you won't make mistakes like this one.
In romaji is onegaishimasu but the problem with romaji is that you don't know exactly where to split the syllables.
The word is written correctly like this:
おねがいします: O - NE - GA - I - SHI - MA - SU
The wrong one that you have is written like this:
おんえがいします: O - N - E - GA - I - SHI - MA - SU
The las one:
Is written in a different writing system called kanji. You should google the 4 japanese writing systems: Hiragana, Katakana, Kanji and Romaji
Finally 神様 in hiragana is written like this way かみさま, the one that you mentioned (カミサマ) is katakana.
In a nutshell, yeah you can write Kanji with hiragana for example 勉強 (Kanji) - べんきょう(Hiragana) - BE-N-KYO-U. Why is this posible? because Kanji is a pictografic writing system this means that any character represent an idea and not a sound (like ancient hieroglyphics) and Hiragana and Katakana are syllables writing systems so you can represent how a kanji is pronounced or written by syllables.