No number in Islam is sacred. However, some number may have some special meanings as number one that points to the God oneness.
No the sacred book of Islam is called The Holy Qur'an
Muhammad was the founder of Islam and the proclaimer of the Qurʾān, Islam's sacred scripture.
The sacred law of Islam is the Shariah law which has been compiled with reference and guidance form the Holy Quran and Hadith
yes
yes i think that the main sacred writing of Islam allow ploygamy
The revelations from Allah were collected and formed the Quran, the sacred text of Islam.
Yes, Jerusalem one of Islam's holiest cities.
Islam's most sacred cities of Mecca and Medinah are in the Kingdom of Saudi Arabia.
What is sacred to both are the Torah, Psalms, and the Old City of Jerusalem.
Hajj provides almost all sacred experiences of Islam.
Al-Qur'an is the sacred book of Islam, which is very important