Breastfeeding

Q: Is your رضاعي nieces رضاعي daughter haraam for you?

E.g. Muhammad and Fatimah are raza'ee brother and sister. Fatimas daugher Zainab, feed Ayesha. Are Ayesha and Muhammad haraam for each other or are they mahrams?

Q: How long should a baby boy be breastfed?

Q: A hadith states لا رضاغ بعد الفصال

Hidaya mentions that the growth from the milk stops after the child's nutrition is changed. If a child was weaned at 8 months due to a 2nd pregnancy, then the mother gave birth and is feeding the 2nd child, can she feed the first child expressed milk?

The child is already weaned, drinking goats milk in abundance. Mothers milk will definitely be more nutritious, but does the hadith mean that it will be prohibited to feed the child who was previously weaned even though it is less than 2 years old ?

Q: How do you calculate two years of breast feeding? Say someone started breast feeding on the 5th Muharram, would the time limit be exactly on the 5th Muharram two years later or do you calculate it like iddat which would result in 24x30=720?