When is a newly introduced act, which achieves real benefit for a large number of Muslims and does not contradict a text, considered a Mursalah (unrestricted public interest) and not an innovation? And is Mursalah limited only to times of need?

The difference between Maslaha Mursala (unrestricted public interest) and Bid'ah (innovation) has been previously clarified. Not everything that contains benefit falls under the category of Bid'ah or Maslaha Mursala. Rather, it is examined: if it fulfills the conditions of Maslaha Mursala, it is considered as such; and if the definition of Bid'ah applies to it, then it is an innovation.