Is it permissible to combine the regular Sunnah prayers (rawatib) with their mentioned proofs, and add twelve rak'ahs at once, based on the hadith: "Whoever prays twelve rak'ahs by day or by night, Allah Almighty will build for him a house in Paradise"?

It is authentically reported in Sahih (definition) Muslim that the Prophet, peace and blessings be upon him, said: "There is no Muslim servant who prays twelve voluntary rak'ahs to Allah every day, other than the obligatory prayers, except that Allah will build for him a house in Paradise." The specification of these rak'ahs has been mentioned in different narrations. In At-Tirmidhi, they are: four before Dhuhr, two after it, two after Maghrib, two after Isha, and two before Fajr. In An-Nasa'i, instead of two rak'ahs after Isha, it is two rak'ahs before Asr. Ash-Shawkani holds the view that one should act upon all that these hadiths contain, even if the number exceeds twelve rak'ahs, in order to attain the mentioned reward. This reward is specific to the supererogatory rak'ahs associated with the obligatory prayers, and any additional prayers are considered good deeds.