Hi Mr Hosein, the MWI of Everett is a philosophical different interpretation than the copenhagian one. That implies other universes and even an infinite number of universes considering the emergent reality and a kind of determinism. The wave function collapse is a main part of this MWI.There is no collapsing for the MWI if my memory is correct.
The other interpretations are interesting too like the born rule, the copenhage interpretation, the qbism,Bohm,.... in fact all this is very philosophical and onmtological and the problems is our limitations about the origin of this reality. The hidden variables, the bell theorem, the spontaneous wave functions collapsings, all this is complex because in fact we have these said limitations.
Personally I consider a pure deterministic reality but with deeper parameters to superimpose and in fact the bell theorem is correct but there are paradoxally hidden variables interacting differently beyond the spectrum of analysis of this GR and actual SM.. We arrive so at an important point considering the main informations primary implying our topologies, geometries, baryonic matter and the GR and the DM and DE. I believe personally that the secret is to unify all and not only the GR and the QFT and QM. THis DM and DE seem essential.