1. qiniyot. As we explained yesterday, the Ashkenazi custom is to refrain from eating rice and any other kind of seeds during Pesaḥ. This is called isur qitniyot (the prohibition of legumes). Now, even though the Ashkenazi custom forbids the consumption ofqitniyot during Pesaḥ, qitniyot products could be kept during Pesaḥ at one's home and there is no need to throw them out or sell them (Rabbi Eliezer Melamed, penine halakha, following SH. A. Rama, 453:1).
Also, as pointed out by Rabbi Eliezer Melamed, although the Ashkenazi custom is to forbid qitniyot during Pesaḥ, that is only when the qitniyot constitute the majority of that product (more than 50%) but if qitniyot are present in a smaller proportion (corn-syrup, corn-starch, etc), the food is not forbidden (see Mishna Berura 8-9).
Now, you can see the book of rabbi Eliezer Melamed, Penine halakha online, here
2. eno hozer vene'or. The Sephardic tradition holds that if a food does not have a ḥameṣ ingredient or by-product in their basic composition, but has a ḥameṣ additive or ingredient in a proportion smaller than 1.6 (or 1/60) of the total product (usually an additive), if that food was elaborated before Pesaḥ, that food is permitted for Pesaḥ. Whereas for the Ashkenazi custom, it does no make a difference if the food was done before or during Pesaḥ: even a minimal amount of ḥameṣ (0.001) renders the whole product non-Kosher for Pesaḥ.
There are many practical consequences to this rule. One of them is that for the Ashkenazi custom every product to be consumed during Pesaḥ has to be done under strict Kosher for Pesaḥ Rabbinical supervision, i.e., in a food factory, the criteria to avoid the presence of ḥameṣ would be, in practical terms, the same as the criteria applied to avoid the presence of an allergen in the food product: a complete ḥameṣ-free environment and the prevention of even an accidental ḥameṣ's cross-contamination.