I want to know about her tough penance. What did her routine during that period ? How she had worshipped Lord Shiva as per Shiva Purana? Did Lord Shiva had appeared as a brahmin & insulted himself in front of parvati? Overall what was the scenario? Please tell me ( if possible, then please provide shlokas in Devanagari from Shiva Purana).
According to Shiva Purana,
1) Parvati performed rigorous penance. The full narrative can be found from Sl.no.29 to 60 of Chapter 22 - Description of Pārvatī’s penance in Shiva Purana.
2) Shiva did appear as brahmin and tried to dissuade Parvati by narrating himself in a negative manner. The full narrative can be found from Sl.nO.12 to 38 of Chapter 27 - Description of the fraudulent words of the Brahmacārin of Shiva Purana.
3) The overall scenario after Shiva's consenting to marry Parvati was happy.