In addition, there are obligations that are to be done by the community and not others.
These are all the main obligations that you need to concern yourself. The fard of your prayer cannot be done by anyone else other than you. There are situations in which the fard of prayer drops from you. Alternatively, if you are so ill that you cannot make ablution or are unconscious for longer than a day.
There is fard amali and fard itqadi. Fard that one has to perform and fard one has to believe in. Disbelief only occurs when someone denies that the fard applies to him and he believes that. If he denies the fard action out of laziness then it does not mean disbelief. Be careful about this!
This is when the performance of a obligatory action causes a danger to ones health or caused extreme hardship. Go through the conditions of performance of the action.
This is a problem which many people ignore. A person who has diabetes or an illness that makes fasting harmful has an an excuse not to fast. Because there is an actual harm to someones health. Maintaining your health is very important. So a person should not fast when there is a danger to ones health and if he fasts he can be sinful for fasting. When the fast is no longer an obligation so a person feeds sixty poor people one meal a day for sixty days. This suffices for his fast and a person should not think he is sinful because he is not.
Like Hajj, if someone is old and in a wheel chair or has a physical disability that does not permit them to go to Hajj without assistance. Then the obligation falls from the person and it is not an obligation anymore. Non performance of the hajj is not sinful in this situation. A lot of parents want to complete Hajj when they are elderly and this can be very difficult. Though it is no longer fard because it is only fard when they have the ability to do without the assistance of another person, the way is safe, they have funds for the trip etc. If people have children and there is no one to look after them, then the parents should not go to hajj. Taking children with one on hajj is a major burden.
If a person does not have the value of wealth to pay zakah, then he does not pay it because it is not an obligation for him.
If a person cannot pray standing up then they pray sitting down. If their illness increases standing then standing would be a sin. So they should sit down. There is no sin in any of these situations. So do not be the super 'rambo' Muslim who makes his illness worse and endangers his life and he is sinful because he did not take the ease. The ease that was given to him by the founders of the four schools.
If one does not know the rulings of a particular matter then they have dispensation until they find out, in a non-Muslim country. But a person who was born in a Muslim country does not have this excuse. The difference being the access to knowledge is not the same. In any case the excuse is invalid once they are informed.