This is where you should have started:
(https://en.wikipedia.org/wiki/Sarawak)Sarawak is a state, not a city, and this is Malaysia's biggest state. It's located on Borneo island which is one of the richest place on Earth in terms of biodiversity because of its jungle/rainforest. Knowing that, you can guess it's very humid and quite hot all year long.
I know that, for Iranians, it's easier to go to Malaysia than many other countries but most of you don't like the country because they don't try to adapt. They think the weather is too hot, local foods are not good, local cultures are stupid... In fact, most Iranians I know are so proud of their culture that they look down at Malaysia. If you come with state of mind, you won't like your stay in Malaysia (or anywhere else).
Your questions sound a bit stupid.
There are foreigners in all countries, even North Korea, it depends what you do or what you want to do in the country. For a simple tourist visit, you won't be allowed to stay long, 30 days I believe but it depends of your passport.
People in Sarawak's cities are no different from other cities, take any city in Iran, can you trust people from that city? It's the same everywhere, most people can be trusted, a few will try to cheat you.
As for the religion, you will find some answers in the wikipedia page. I will just say that Malaysia is not like Iran, no one will force you to follow religious practices, at least, it applies for foreigners.