Witr and Nawaafil

Witr Salaah

Q: I prayed witr salaah with three rakaats. Meaning, my witr is similar to magrib salaah but with a Surah and then duaa qunoot in the third rakaat. Is this the correct way of reading witr salaah?

Sunnats after zuhr

Q: I started praying the 12 Sunnahs prayer. However, I want to pray four rakats after Dhur and not two because four is recommended. Are the four rakats after Dhur with two tasleems like the four rakats before Dhur?

Salaatut taubah

Q: Are there any particular Surahs or zikr/tasbeeh to be recited during istighfar Salaah? Because in one book I read it says that one should perform istighfar salah two rakaats by reciting Surah qadr after Surah Fatiha and recite Astaghfirullah 140 time in total. Is this true? Is this the way it should be performed? Please clarify and guide me.