Peace be on the followers of guidance,
Praise be to God.
Thank you for asking your question anonymous. Please ignore the first post about the taliban, I think that person is just trying to scare you away from Islam.
Let me see if I can help you with your questions:
1.) Allah: Allah is the One God of the whole Universe, He is the God of Abraham, Moses, Jesus, and Muhammad. There is no god but He. Allah is the word used by Arabs for God, whether they are Christian, Jewish, Muslim, or pagans.
The difference is that Muslims worship Allah alone, with no partners, and perfect His names and attributes. While other religions, through the passing of time, attribute human qualities to Allah, such as children, opposites, etc.
Interestingly, I have an Aramaic manuscript of some parts of the Bible, and the world Allah (الله) is written nearly identically in both Arabic and Aramaic, so Allah is closer to the actual word used by Jesus and Moses, peace be upon them, then the word 'God'.
You are certainly welcome to use the word Allah. Perhaps some Muslims feel bad when non-Muslims use the word Allah in a negative manner or to mock Islam.
2.) Asalamualaikum means: "peace be with you". It is the greeting of Muslims. It is a prayer, a noble greeting, that was taught to Adam by the angels.
An interesting story: during the time of the Prophet, pbuh, some Jewish people used to twist the words Asalamualaikum, in a way that meant "May poison be upon you."
While the Prophet pbuh was walking with his wife Aisha, a Jewish person greeted the Prophet with the latter greeting. His wife, Aisha, become very upset and said to the Jew: "May the curses of God be upon you and His Wrath and Anger!"
The Prophet, the noblest of human beings, said to Aisha: "Take it easy." She said, "Didn't you hear what he said to you?"
The Prophet replied, "Yes, and I simply replied, 'And to you also.'
The Prophet then added, "Kindness is never added to a thing, except that it beautifies it. And kindness is never absent from a thing, except that it leaves it deficient."
May Allah guide you to Islam, and please feel free to ask any other questions that you may have.
And Allah knows best.