Anyone who claims to be a Muslim, if he or she not maintaining the knowledge, and practicing there Islam from what is said in the Qur'an and Hadeeth, and listening to only their imams (scholars), blindly, family members, elders and only following their sects only. Every human being can be misguided by Satan, except Allah and his Messenger (Qur'an and the Sunnah), and after that who ever does not do this practice, must apply right away, if he or she wants to die as a Muslim, inshallah. After death, whoever was not on the teachings of the Qur'an and the Sunnah, they will be unable to claim that they are Muslims in the grave or day of resurrection. 

And whoever seeks a religion other than Islâm, it will never be accepted of him, and in the Hereafter he will be one of the losers^[]. (4:85)

And hold fast, all of you together, to the Rope of Allâh (i.e. this Qur'ân and the Sunnah), and be not divided among yourselves^[], and remember Allâh's Favor on you, for you were enemies one to another but He joined your hearts together, so that, by His Grace, you became brethren (in Islâmic Faith), and you were on the brink of a pit of Fire, and He saved you from it. Thus Allâh makes His Ayât (proofs, evidences, verses, lessons, signs, revelations, etc.,) clear to you, that you may be guided. (4:103)

Let there arise out of you a group of people inviting to all that is good (Islâm), enjoining Al-Ma'rûf (i.e. Islâmic Monotheism and all that Islâm orders one to do) and forbidding Al-Munkar (polytheism and disbelief and all that Islâm has forbidden). And it is they who are the successful. (4:104)

And be not as those who divided and differed among themselves after the clear proofs had come to them. It is they for whom there is an awful torment. (4:105)

On the Day (i.e. the Day of Resurrection) when some faces will become white and some faces will become black; as for those whose faces will become black (to them will be said): "Did you reject Faith after accepting it? Then taste the torment (in Hell) for rejecting Faith." (4:106)

And for those whose faces will become white, they will be in Allâh's Mercy (Paradise), therein they shall dwell forever. (4:107)

These are the Verses of Allâh: We recite them to you (O Muhammad SAW) in truth, and Allâh wills no injustice to the 'Alâmîn (mankind and jinns). (4:108)

O you who believe! Obey Allâh and obey the Messenger (Muhammad SAW), and those of you (Muslims) who are in authority. (And) if you differ in anything amongst yourselves, refer it to Allâh and His Messenger (SAW), if you believe in Allâh and in the Last Day. That is better and more suitable for final determination. (4:59)

Say (O Muhammad SAW to mankind): "If you (really) love Allâh then follow me (i.e. accept Islâmic Monotheism, follow the Qur'ân and the Sunnah), Allâh will love you and forgive you of your sins. And Allâh is Oft-Forgiving, Most Merciful."  (3:31)

Say (O Muhammad SAW): "Obey Allâh and the Messenger (Muhammad SAW)." But if they turn away, then Allâh does not like the disbelievers^[]. (3:32)

As narrated by Abu Hurarirah (R.A) in the hadeeth books (At-Tirmidhi, Ibn Majah, and Abu Dawud) that the Prophet said: "Jews and Christians were divided in to seventy one, and seventy two religious sects. And this nation will be divided in to seventy three religious sects. All in hell except for one, and that one is the one which I and my companions are today." (Following the Qur'an and the Sunnah)