first thing what Allah said in quran
“…This day have I perfected your religion for you, completed My Grace upon you, and have chosen Islam for you as your religion…” (Quran 5:3)
34:28 We have not sent thee (prophet mohammed) but as a UNIVERSAL (Messenger) to men, giving them glad tidings, and warning them (against sin), but most men understand not.
if u say 786 is bismillaha then your going against quran and prophet mohammed said
O People, no prophet or apostle will come after me, and no new faith will be born. Reason well, therefore, O people, and understand words which I convey to you. I leave behind me two things, the Quran and my example, the Sunnah, and if you follow these you will never go astray.
All those who listen to me shall pass on my words to others and those to others again; and it may be that the last ones understand my words better than those who listen to me directly. Be my witness, O God, that I have conveyed your message to your people.”
its clear from here that no new teaching will be taught
if u say 786 is bismilla ur going against prophet mohammed
786 is nothing in islam