bitul before pesach

Question

1) can one lechatchila be mevatel chametz in a taaruvot before pesach. i.e. can one mix bread crumbs into a thick stew before pesach and consider it batul and eat it on pesach? 2) i thought that liquids in liquids (lach b'lach) are batul in sixty midoraisa (biblically) so how is corn syrup in the soda batul in rov? thank you