Is buying shared land from someone who has taken possession of it considered halal or haram?
The shared land is possessed by the country i.e. for all people; therefore, it shouldn't be possessed/occupied save by it's guardian/owner permission,thusly it can't be possessed save by having owners' permission. Finally, buying it from a person who don't possess it is impermissible. And Allah Knows Best.
Is performing Umrah an obligation for who is capable. Is he accountable for not performing it in this case?
Umrah is an obligation once in a lifetime for every Muslim. When physical and financial ability is present, it is preferable to perform Umrah, as well as Hajj. If one can afford to perform Umrah but not Hajj, then they should begin with Umrah, especially since Hajj nowadays is not accessible to everyone who wishes to perform it. In contrast, Umrah is more open and easier to undertake. And Allah knows best.
If the fasting of nine years has accumulated upon me, I wish to make them up by dividing them over several years, as it is difficult to fast them all in one year due to their large number. Consequently, expiation will be due on me. Is it permissible to pay the expiation after completing all the make-up fasts, even if it takes years?
If the fasting was broken due to a valid legal excuse, it is permissible to divide the make-up fasts over several years based on one’s ability. However, if a person passes away before completing the make-up fasts, the heirs must fast on their behalf or feed one needy person for each missed day.
If the fasting was broken without a valid excuse, one must hasten to make it up. Should the person die before completing the make-up fasts, the heirs must either fast or feed the needy on their behalf. As for the expiation, it is calculated after completing all the make-up fasts. And Allah Knows Best.
What should a praying person who doubts having offered one, or two prostrations in the third Rakah (unit of prayer) do?
Whoever has doubts about their prayer should consider what is less i.e. the above person should offer another Sajda (prostration) and complete his/her prayer, then offer Sujood As-Sahw (prostration of forgetfulness). And Allah Knows Best.