I have beaten the mixture only two times, once while folding in the pistachios and then after two hours. If you beat at least four times in two-hour intervals, it would have a smoother texture. Nonetheless, it was fine.
Cardamom is for flavoring. If you don't prefer it, you can use cinnamon or vanilla extract.
Use full fat coconut milk - low fat would definitely not give the same texture.
I have used Badami mangoes. You can use any variety of your choice. But adjust sugar as per sweetness.