"When reciting the Quran silently, must all the rules of Tajweed, including the lengths of vowels (madd), nasalizations (ghunnah), and assimilations (idgham), be observed, and what are their types? "

Praise be to Allah, it is incumbent upon the Qur'an reader to recite and perfect it. The prevailing opinion regarding the ruling of tajweed is that what is obligatory from it legally is the preservation of the pronunciation of letters and their articulation points without altering or changing the meaning. Anything beyond that is recommended. Scholars have differentiated between what is a legal obligation (such as preserving the meaning and structure) and what is a technical obligation (such as assimilation and concealment). Neglecting the legal obligation incurs sin, whereas there is no sin in neglecting the technical obligation. Regulating the lengths, nasal sounds, clarity, and assimilation are technical obligations and not legal ones.