Gayawi, invisible, or unseen subjects are things which can not be understood by knowledge and sense. Such is the existence of Allah, His revelation, Paradise and Hell, the angels, the torment of the grave and the resurrection of the dead body etc. From this it appears that believing in what is said by Allah and His Messenger (peace be upon him) is also a part of the faith which can not be realized by knowledge and sense. And denying it disbelief and deviation.
[2] To pray properly or to establish Prayer means to take care of the prayer according to the guidance of the Prophet (pbuh) regularly. Otherwise the hypocrites would also pray.
[3] The term 'spent' is broad; In order to include both the obligatory and non-performing forms (expenditure, cost, charity or charity) Believers do not have any kind of mischief on the basis of their ability. Even spending on this "spent" money spent on parents and family and children is also the means of attaining goodness.