You do not need to pay khums under these conditions.
The itinerant distance is the criterion for the calculation of distance in religious issues. The reason for this ruling is that what could generally be understood from traditional proofs (ḥadīths) is the itinerant distance which is calculated based on the normal way traversed by people. This is particularly emphasized because usually the direct way between two locations is shorter than the normal itinerant distance between them that people usually wend. Therefore if the direct way were the criterion for calculating distance in religious issues then it should have been explicitly mentioned in narrations.
If the same illness led to his death and he was not able to perform the qaḍā of his prayers and fasts then there is no need to perform their qaḍā. However, if he regained his health and was able to perform them but he did not, it is obligatory on his elder son to make up for them. But those that he had performed incorrectly although it is not obligatory for his elder son but he had better perform their qaḍā.
They can perform the prayers simultaneously.
Perform the number of prayers that you are certain you have missed with the intention of obligatory qaḍā and if you want to perform more than that, perform them with the intention of precautionary qaḍā.
This person can perform qunūt after rukū‘ and then go for sajdah without rukū‘ and continue the prayer.
1- It is not permitted. 2- It is like the previous issue. 3- Yes, you can ask all religious lawful matters from Allah.
None of them is necessary and the verbal declaration of the intention is not permissible as an obligatory precaution.
Travelers have the right to perform their prayers in al-Masjid al-Harām and al-Masjid al-Nabawi and also all of Mecca and Medina complete or shortened and complete prayer is better and there is no difference between old and new parts of Mecca and Medina.
It is permissible.
This act is makrūh (abominable) unless this is the only way of having presence of the heart (full concentration).
If it is not too difficult for them, they need to perform their prayers in standing position, even though they do it by using a cane and the like. However, if it causes them much difficulty and discomfort, they can perform their prayers in a sitting position.