Is it true that whoever prays twelve voluntary rak'ahs for the sake of Allah will have a house built for him by Allah in Paradise, and is it permissible to pray them all at once, and will Allah build a house for the worshipper in Paradise every day if he persists in that?

Whoever prays twelve voluntary Rak'ats every day, Allah will build for him a house in Paradise. Other hadiths have explained these as: four before Dhuhr, two after Dhuhr, two after Maghrib, two after Isha, and two before Fajr. The reward also includes whoever prays this number all at once, whether by night or day. This is from the bounty of Allah Almighty.