What should a sick person, who is incapable of fasting, and who didn`t make up for missed fasting days, do?

One who has missed fasting days is obliged to make up for them, but if he/she wasn`t able to because of an incurable disease , or old age, then he/she has to pay a ransom which is feeding a needy person for each of the missed fasting days. And Allah Knows Best.

Is it permissible to make up missed prayers at the times in which praying is disliked?

All perfect praise be to Allah,The Lord of The Worlds                                                                                                                                                                        It is permissible to make up missed prayers at any time even that in which praying is disliked. Absolute supererogatory prayer is forbidden to be performed at the times in which praying is disliked, and this also applies to Ihram and Istikhara prayers. However, there is no harm in offering prayers in Mekah during those times. And Allah Knows Best.

Is Zakah (obligatory charity) due on leased property, and how is it calculated?

Zakah isn`t due on the leased property itself, but on the saved income from that property if it reached Nissab (minimum amount liable for Zakah), and a whole lunar year had lapsed over saving it.

In life insurance with the Potash Company, enrollment is mandatory, and employees have the right to receive a cash amount from the insurance for surgeries and illnesses while employed by the company. Is the amount given by the insurance in this case permissible (Halal) or prohibited (Haram)?