Entering Islam in its Entirety is obligated

O you who believe! Enter Silm perfectly, and follow not the footsteps of Shaytan (Satan). Verily, he is to you a plain enemy. Then if you slide back after the clear signs (Prophet Muhammad , and this Qur’an and Islam) have come to you, then know that Allah is All-Mighty, All-Wise (2:208-209)

Tafsir (Ibn Kathir)

Entering Islam in its Entirety is obligated

Allah commands His servants who believe in Him and have faith in His Messenger to implement all of Islam’s legislation and law, to adhere to all of its commandments, as much as they can, and to refrain from all of its prohibitions. `Al-`Awfi said that Ibn `Abbas said that Allah’s statement:

(Enter Silm) means Islam.  Allah’s statement:

(…perfectly) means, in its entirety. This  Ayah means, `Perform all the good works and the various pious deeds, this is especially addressed to those from among the People of the Scripture who embraced the faith.’

Ibn Abu Hatim reported that Ibn `Abbas said that: (O you who believe! Enter Silm perfectly) refers to the believers among the People of the Scripture. This is because they believed in Allah, some of them still followed some parts of the Tawrah and the previous revelations.

Allah then said:

(…and follow not the footsteps of Shaytan) meaning, perform the acts of worship and avoid what Satan commands you to do. This is because:

He (Shaytan) commands you only what is evil and Fahsha’ (sinful), and that you should say about Allah what you know not. (2:169) and:

He only invites his Hizb (followers) that they may become the dwellers of the blazing Fire. (35:6)

Hence, Allah said:

(Verily, he is to you an open enemy.)

Allah said:

(Then if you slide back after the clear signs have come to you) meaning, if you deviate from the Truth after clear proofs have been established against you,

(…then know that Allah is All-Mighty) in His punishment, and no one can escape His vengeance or defeat Him.

(All-Wise) in His decisions, actions and rulings.  He is Mighty in His vengeance, Wise in His decision.