Can a Mukallaf who has knowledge of the rulings of different Marajeʿ, integrate between them and not to refer to a certain Marjaʿ?

There are a number of common principles in the aspect of religious Ijtihād which a Mujtahid must have knowledge of, and it is not possible for one to be a Mujtahid, without having a general and holistic understanding of religious knowledges. Of course, one may be aware of the details of jurisprudential issues or may have more conversance in the issues of belief or its branches and its minutiae, but this does not imply that he has the complete knowledge about basis and foundation of Ijtihād. Therefore, if there is a person with a greater understanding of jurisprudential issues or belief, provided that his Fatawās are consistent with the principles of religious ijtihad, one can integrate his Fatawās with other ones.