Is it incumbent on a father to cover the marriage costs of his son if the latter couldn`t afford them?

The son should seek the help of his relatives in order to convince his father to do the aforesaid, and the father should make sure that his son doesn`t commit fornication through helping him to get married, and Allah will reward him for doing so.

What is the ruling on someone who doesn`t perform prayer?

All perfect praise be to Allah,The Lord of The Worlds                                                                                                                                                                    Not performing prayer is a major sin, and one who doesn`t pray out of laziness is considered an oft-sinner ;whereas, the one who denies that it is mandatory is considered a disbeliever. And Allah Knows Best.

Is fasting obligatory for a child?

 

What is the ruling on someone who eats or drinks while uncertain about the arrival of dawn, then later finds out that dawn had not yet broken?

If a person does this, their fast remains valid, as it is confirmed that they ate during the night. Similarly, if someone eats while uncertain and remains unsure whether they ate before or after dawn, their fast is still valid. This is based on the maxim of Sharia Law, which states: "Certainty is not removed by doubt." Certainty, here, is the presence of night, and the doubt concerns the arrival of dawn. Therefore, one relies on certainty and disregards doubt.