Praise be to Allah.
1 – If it is gold or silver, then zakaah has to be paid on it. To be certain of what it is, you should consult the experts in that field.
2 – This mark does not necessarily appear on the forehead of every person who prays. Rather people vary in the nature of their skin, and the fact that it appears does not mean that a person is righteous. The well-known view among the mufassireen is that the phrase “The mark of them (i.e. of their Faith) is on their faces” refers to the light of obedience.
3 – You have to read Soorat al-Baqarah in the house once a day for three days.
4 – Strive in making du’aa’ for your brothers there, that Allaah may answer your prayers; and give charity to them as much as you can.