Subhan Allah means declaring Allah to be above every bad thing. Wa bihamdihi means combining tasbih (glorification) and hamd (praise). For more, please see the detailed answer.

Islam encourages frequent Istighfar (seeking forgiveness), and the Prophet Muhammad used to seek forgiveness up to 100 times a day. However, setting a fixed number beyond what is narrated in authentic Hadiths is not obligatory. Instead, a Muslim may engage in Istighfar as much as they can without restriction.