help an incoming freshie out

Before UPCAT, I was undecided on which course to pursue. In my application, I put BS Chem as my first choice. Fortunately enough I passed UPCAT and after the results were out, that was the only time I came up with BS Business Economics as my preferred course. I'm aware that I must go through BS Chem for a year and that UPSE requires Math 17 and a 2.25 GWA for those who want to shift. I know that there is no guarantee that I would be able to shift after a year, that's why I consider entering UP as a gamble I'm willing to make. I don't want to end up being locked up in BS Chem.

Now here are my questions:

1. Apart from the GWA, what other factors could hinder shifting?

2. Are shiftees regarded as inferior to those who are in that course since first year?

3. Can shifting affect my employability in the future?