Since macroscopic objects have more particle like nature and they are always being observed (interact) with their surrounding, does MWI also applies here and if yes then what is its significance. Is it possible that in different worlds I have different life- like President in one of them. Also I read somewhere that in our world matter is preferred over antimatter during the beginning of the Universe and there must be another parallel Universe in which antimatter is preferred over matter. Does this mean that really another Universe exists?
Since macroscopic objects have more particle like nature and they are always being observed (interact) with their surrounding, does MWI also applies here and if yes then what is its significance.
In the many worlds interpretation, interactions that record information about a system prevent interference between different versions of a system. Such interactions include measurements. This effect is called decoherence, see
There is no collapse. Multiple versions of the system continue to exist after the measurement, but they don't interact with you so you can't see them.
All of the universes in the multiverse obey the laws of physics. It may be the case that in some other universe there is somebody who resembles you in many respects and is president. This seems compatible with the laws of physics as far as I know. It is conceivable that there is an anti-matter universe, but I don't know the relevant laws of physics well enough to be able to tell.
The MWI is what you get when you assume that the time dependent Schrödinger equation applies to all systems, no matter how large. This means that wavefunction collapse after a measurement is only an effective description, the exact description involves a superposition where the observer exists in different states experiencing different outcomes, the observer is then entangled with the system. Such a superposition cannot in practice be distinguished from a situation where only one outcome is realized.