1. Reality is advaita - it means single being or whole cosmos is one being.
2. Maya or illusion is 'consciousness without above knowledge'. This is a cause of suffering.
3. As long as you're in illusion, you will suffer because you consider yourself different than others. It is called 'I". As long as there is 'I', you're in Maya. 'I' give rise to you/he/she/they/animals. If idea of 'I' is not there then no you/he/she/they. All becomes one. I guess Douglas Hofstadter tried to explain same concept in GEB by using self-referential systems. (I might be wrong as I never able to finish book).
4. Enlightened Guru is very important in journey. Creation is considered as dense forest. Without Guru you can lose yourself. Guru appears when Chela is ready. You have to keep searching truth.
5. Law of Karma - Whatever is your current situation is your karma. How do you react to it is your free will ?
6. Creation is spontaneous per say. There is no reason behind it.
7. People can use different practices as per their nature to reach pt 1.
8. As long as there is desire, reincarnation will happen. Now problem is you may be man/woman/animal/cow in next birth. So treat everyone well (including species other than human being). You come in contact with different people (good or bad)/animals because of some relation (may be in previous birth).
9. Cow is considered sacred as she has human like emotions. She can live happily without human help but still she gives human everything even after treating her bad. It is considered great sacrifice e.g giving milk of your child to other species.
What I like most is considering whole universe as family. Sometimes I feel sad as being human. Also I found many stoicism concepts in Hindu philosophy which is very interesting. 2 completely different cultures are on same conclusions.