The Philosophy of Ethics

If I were an atheist, I wouldn't follow my religion's belief system, but rather another pre-existing one or create my own. People think that the fear of hell and eternal damnation prevents them from committing crimes, but they don't give enough credit to their humanity. Even without the fear of the afterlife to deter me from crimes, I'd still have friends and family's expectations to live up to.

If God is omniscient and already knows my future actions, why would it matter how ethically I act? It's futile if I try to be conscious of my actions since I'm already following a definite path. Why try to be morally good and reason through dilemmas when I can do whatever I want to do and let fate take the lead. However, if God is real and therefore watching me, I'd want to act my best.

Everyone is obligated to take care of the environment because how you leave it will impact future generations. I like to follow Indigenous 7th Generation Principle about taking responsibility for the environment as it's disrespectful to the future generations to leave it any other way but clean. Every single person should take responsibility for how they leave the land for the next 7 generations.
Corresponds with the Samma-Kammanta rule (taking the right action by taking care of the environment).

I'd take pictures of the test, but only keep them to myself because my teacher would get suspicious if everyone in the class did exceptionally well, and thus call foul play. The ethical code I'm following here is that I know that I am not harming anyone and the decision I'm making is one that can't hurt me if reciprocated. Plus, if I simply stumbled across the papers, who am I to deny fate? It's not like I sought the papers out, then that would be immoral. Also, the reward for cheating is very high (a good mark!! on a math test too!).
Does not abide with rule 4 of Islam's 1o commandments -- "do not indulge in shameful acts."

I would return the money because the money that cashiers lose is often reduced from their own paychecks. I wouldn't want someone to lose part of their income over a simple mistake, and I'd hate it if it happened to me (the golden rule: Do unto others as you would have them do unto you).

Deontological Ethics
The rule that overlaps between the Islamic and Christian 10 Commandments as well as the Seven Laws of Noah is not to steal. The Qur'an specifically states that one must be fair and "should always be mindful of doing business in an honest way."

By utilitarianism rules (welfare and happiness of others), I'd donate the majority of the money. Since in this scenario, I'm well-off and presumably middle-high class, the money would support fundamental humanist causes and contribute to the wellbeing of many people.