Big-O complexity when c is a tiny fraction
Medium answer - yes. As you said for the previous case, in the long run $n^4$ outpaces all of them. This is still true despite the constant in front.

Check it out: plot.

Also, remember that $n^3$ and $n^4$ are both $O(n^4)$, and in fact are both $O(n^{10})$ because big-O is an upper bound. So you might ask "is there any tighter big-O bound on this function than $O(n^4)$, like $O(n^3)$, and the answer would be no.