The main reason is that denying any of the five pillars intentionally by any Muslim expels him out of Islam religion and considers him/her non-Muslim. Refer to questions below.
The five pillars structure Islam and the daily lives of Muslim's, because Muslims believe that without them their lives would not be complete and they would not earn Gods trust, it's like a building would not be able to hold itself up without the foundations/pillars in this case pillars, the Muslim's believe that the five pillars are what hold their lives and Islam up.
because they are rules on how muslims should live thier life.
yes
for example Resurrection is one of 5 pillars this pillar is very effective because we work for god not for vale and believe that the god see human and will punish or encourage in Resurrection
Believing in the five pillars is a must for a Muslim. He is also required to act upon these pillars. Anyhow, if a Muslims does believe at heart in the 5 pillars but is slack in practising them, he may repent at any time. Allah Almighty is Oft-Forgiving, the most Merciful.
All Muslims. Refer to related question below
Prophet Muhammad (PBUH) was given the five pillars by inspiration from Allah (God in English) through the angel Gabriel (Jibril). This explains that these pillars are stated in Quran too.
For many reasons; mainly:It is the third pillar of Islam five pillars to be followedIt is a demonstration of social solidarityIt is to be rewarded by GodRefer to question below
Hajj is not a person. It is a pilgrimage made by Muslims because it is one of the 5 Pillars Of Islam
Muslims know and believe that following the Islam 5 pillars is a chracteristic of the Muslims. Who abandons following any of the Islam 5 pillars, intentionally, is not only sinful but also is no longer considered Muslim.God is All-Merciful. Who committed this sin should be confident that God may accept his repentance if he intends heartily that he will follow the five pillars without any denial.See for more information the related question below.
realign is a path which you will stay on for all your life for example for Muslims there path is the 5 pillars and for siks there is the 5 ks
Fasting Ramadan (Sawm) and performing pilgrimage (Hajj) are the fourth and fifth pillars of the five Islam pillars. Refer to question below.