Are my actions in changing the intention of Hajj from Ifrad to Qiran then to Tamattu valid, and is my Hajj thereby valid?

The questioner stated that he entered into ihram for Hajj Tamattu', then incorporated Hajj into 'Umrah before starting the tawaf, thus becoming a Qarin (performing Hajj Qiran). This is permissible according to the four schools of thought. Then, on the day of Arafat, after standing there, he dissolved the Qiran into an 'Umrah. This is not permissible according to the four schools of thought. The Hanbalis only permitted a Qarin to dissolve his Qiran into an 'Umrah on the condition that he had not yet offered the sacrificial animal (hady) and had not yet stood at Arafat.

Therefore, dissolving the Qiran after standing at Arafat is incorrect. You are considered to have remained in your ihram for Qiran. Since you performed the Tawaf al-Ifadah, your Hajj is valid and there is nothing against you, provided you fulfilled the remaining rituals such as staying overnight in Mina, stoning the Jamarat, and other obligations. However, you owe a fidyah for the prohibitions you committed that are destructive in nature, such as shaving hair and clipping nails. As for prohibitions related to comfort, such as wearing sewn garments or using perfume, there is nothing upon you due to your ignorance. The fidyah is to slaughter a sheep in the Haram, or to feed six poor persons half a sa' of food each, or to fast for three days.

It is appropriate that only scholars be consulted regarding শরia rulings, for Allah says: (So ask the people of the message if you do not know).