Carrying and burying the deceased

Q: Please explain the following:

1. Is a grave sacred land?

2. Is it best for it to be flat with no heap of sand rising?

3. Should a grave be unmarked with no plank or name-plate or is it better to have it to help identify where a person is buried?

4. Can flowers etc be planted on a grave?

5. Is there reward in spending money on maintaining a cemetery including removing weeds from the graves?

Q: Can a son in-law go in the grave to bury the mother in-law?

Q: Can a mother and child who passed away together in an accident be buried in one grave?

Q: What will be the role of a husband after the death of his wife? Can he give shoulder to the Mayyit?

Q:  Is it better to raise the graves a little like that of a camels hump or better to flatten it like how its done in Jannatul Baqee?

Q: 

1. Should one sprinkle water on the qabr after burial? Many people do so. What is the shar'ee hukm?
2. If plants grow on grave should they be cut?
3. Should one put a twig on the qabr?
4. People look at the mayats face and delay the burial. What should be done?
5. Is there any Hadith regarding recitation of the first and last ruku of Surah baqarah after burial and also what is the hukm of dua in congregation after burial?

Q: Last year my father passed away in Pakistan. Because of the rain, my father's grave opened. Can we put soil in the grave or is there another solution? Please guide us.

Q: Covering the janazah of a woman, how did it start?

Q: Is there any authentic hadith from the books of hadith about the forty steps for each person to carry the janazah?

Q: The children who die while in the wombs. Is it necessary to bury them in the qabrastan or anywhere else (for example; garden, backyard etc)?