Hi there, to answer your question,
1. Gelas here refers bekas untuk minum as you mentioned. However biji here is used specially for oenjodoh bilangan, it is not the same with biji (noun)
2. As in question 1, this is also the case, batang here does not refer to something called batang like batang kayu (wood pole), but this is one of the special cases in penjodoh bilangan.