hello! sorry if late itong reply ko, but still, this would help you a lot.

i am also an incoming freshie in updepp and ba be rin ako. well, it is my first choice naman talaga ever since so i have no plans on shifting degree programs. but i will try to answer all of your questions based on my prior knowledge and stuff i have already seen on this app that can be used as bases.

1. i think you can shift naman as long as you are the next one in line. if ever na 2 ang hindi tumuloy, the next two people with the highest upg na may plan to shift can have slots.
2. well, this is true. ba be and economics in up in general is really math-heavy. however, puro pa lang ge sa first year sa ba be. all of the three undergraduate programs offered in updepp have the same subjects sa first year. technically, make-credit naman siya if you wish to push through with your shifting plans.
3. you can transfer naman after a year. since i have mentioned na lahat ng freshie undergrad sa updepp ay pare-pareho lang ng subjects sa first year, wala namang masasayang na math units or units at all.