Recall that in a single processor system, parallel execution is an illusion. One instruction from one process at a time can be executed by the CPU even though multiple processes reside in main memory. Imagine a restaurant with only one waiter and few customers. There is no way for the waiter to serve more than one customer at a time but if it happens that the waiter is fast enough to rotate on the tables and provide food quickly then you get the feeling that all customers are being served at the same time. This is the example of time sharing when CPU time (or waiter time) is being shared between processes (customers). Multi programming and multitasking operating systems are nothing but time sharing systems. In multi programming though the CPU is shared between programs it is not the perfect example on CPU time sharing because one program keeps running until it blocks however in a multitasking (modern operating system) time sharing is best manifested because each running process takes only a fair amount of the CPU time called quantum time. Even in a multiprocessing system when we have more than one processor still each processor time is shared between running processes. As you can see all terms are somehow related in one way or another however not using the right term in the right context is what makes the confusion so keep that in mind.
It is not permissible to pray behind one who is like this, and if one who knows that the belief of the imam is like that prays behind him, his prayer is invalid, because most of the things listed are characteristics of kufr (disbelief) and bid‘ah (innovation) that are contrary to the Tawheed (affirmation of the Oneness of Allah) with which Allah sent His Messengers and which He revealed in His Books. It is contrary to the clear meaning of the Qur’an, such as the verses in which Allah, may He be exalted, says (interpretation of the meaning): “Verily, you (O Muhammad ) will die and verily, they (too) will die” [az-Zumar 39:30] and “And the mosques are for Allah (Alone), so invoke not anyone along with Allah” [al-Jinn 72:18]. The innovations that they do should be denounced in a gentle way; if they accept it then praise be to Allah. If they do not accept it, then shun them and pray in the mosques of Ahl as-Sunnah. We have a good example in the Close Friend (Khaleel) of the Most Merciful, as Allah tells us he said (interpretation of the meaning): “And I shall turn away from you and from those whom you invoke besides Allah. And I shall call on my Lord; and I hope that I shall not be unblest in my invocation to my Lord” [Maryam 19:48].
Pain or discomfort in the chest area is certainly a cause for concern because it can be a sign of lung (or heart) disease. However, more often than not, most pain experienced in the upper torso is caused by far less serious issues, such as indigestion, acid reflux and strained muscles. Differentiating pain caused by a lung condition from that caused by a pulled muscle can be straightforward if you understand the common telltale symptoms of each issue. If you have any doubt as to what's causing your chest pain, particularly if it's getting worse or you have cardiac risk factors like diabetes, high blood pressure, high cholesterol, or obesity, make an appointment with your doctor as soon as you can for a thorough physical examination.