Assalmu alaykum shakyh, 1. The Hadith of the messenger SAW: "مَنْ أَحْدَثَ فِي أَمْرِنَا هَذَا مَا لَيْسَ مِنْهُ فَهُوَ رَدٌّ Is the ما here not also a generality meaning whatsoever. Would that be correct to say or not?

Ustadh AbdulAziz al-Haqqan

It is general as it refers to ism mawsool (allathee).