To Consume Brewer's Yeast
There is no objection to consuming brewer's yeast unless it is intoxicant.

Right of Passers-by to Tree Fruits 
One may eat the fruits of a tree which grows in a road or a tree some of whose branches came out of the garden provided that: a) he does not go there to eat the fruits, b) he does not harm/damage a part of the tree and c) to eat there and does not carry the fruits to another place.

Gelatin Imported from Non-Islamic Countries
One may eat food containing gelatin provided that one knows it is obtained from the bone of a ḥalāl meat animal like a cow.

Doubted Gelatin
To transform materials from religiously edible or non-edible animals into gelatin is not categorized as istiḥālah (metamorphosis). But, if there are two — ḥalāl and ḥarām — types of gelatin and you do not know the one you want to eat belongs to which group, it is ruled to be ḥalāl.