No, Sunnah prayers are highly recommended. And Nafl prayers are recommended and added benefit.

On the day of judgement, 1st action counted will be 5 daily prayers, if they are lacking in count or perfection, the Allah will ask to see if My servant has supplementary prayers to make up the weight in positive for a person. Also I have experienced that when I pray supplementary prayers, I feel closer to Allah and I improve my perfection in prayers.

I'm sure there are other rewards, but this is what I can think of right now.

The linguistic meaning of QADA is compensation.

Revelation, quran and Sahih hadith speak of compensation for a single obligatory prayer or a few obligatory prayers which have been missed due to unavoidable circumstances.

Since witr and sunnah of fajr do not fall under obligatory prayers they cannot be compensated. They cannot be made up if you have missed them unintentionally.

Secondly, the reward system of Allah is so beautiful that if a person prays 28 sunnah of fajr in a month and missed sunnah on a random day because of sleep or unconsciousness, Allah willing his reward is written as if he has prayed the sunnah.

Eating Suhur is Sunnah. Not obligatory. As Prophet Muhammad (Salla-Allahu-Alaihi-Wa-Sallam) Says,

"Eat Suhur (predawn meal). Surely, there is a blessing in Suhur."

^{Source: This hadith from Bukhari and Muslim}

But, Keeping Fast during Ramadan is Obligatory for every Muslim. As described in the Quran and many Ahadith of Prophet (Salla-Allahu-Alaihi-Wa-Sallam).

The Ayat from Quran is

The month of Ramadhan [is that] in which was revealed the Qur'an, a guidance for the people and clear proofs of guidance and criterion. So whoever sights [the new moon of] the month, let him fast it; and whoever is ill or on a journey - then an equal number of other days.

^{Source: Sahih International Translation of The Holy Quran}

So, the conclusion is, Even if you missed Suhur, You have to fast. Suhur is not obligatory and it is a Sunnah and Prophet says, there is Barakah (blessings) in Suhur. But, it is not in the per-requisites of Fasting

Hope this will help