Tell me if I'm wrong, but I think you want to know how to invert subject/verb in questions while using "Est-ce que" or "n'est-ce pas" to formulate the question.
If so, please note the following:
1) You need to invert subject and verb if you ask the question without those expressions, e.g.:
Aimes-tu voyager ? Oui, j'aime voyager.
2) If you decide to use "Est-ce que" to create your question, then there is NO inversion, e.g.:
Est-ce que tu aimes voyager ? Oui, j'aime voyager.
Note: You add "Est-ce que" at the beginning of the afirmative sentence, which makes it interrogative.
3) Almost the same goes for "N'est-ce pas", except you add it at the end of the sentence, e.g.:
Tu aimes voyager, n'est-ce pas ? Oui, j'aime voyager.
Note: In that case, you ask the question but you have an idea of the answer. You're asking for a confirmation.
For "D'accord", I don't think it's really used. It seems more like an English expression literally translated into French.