Is saying (something is) "more better" grammatically correct?

I would say no.. just saying something is better not only gets the point across but i believe it is grammatically correct

nope

That is not gramatically correct.

More and most are used for longer words such as "beautiful", not "good".

good -> better -> best

beautiful -> more beautiful -> most beautiful

You do not mix the two, like "complicater", "more cooler" or "most horriblest"