the trimetrical classic (三字經) is extracted from ancient confucianism literatures, in three characters verses.
the eight verses in question are derived from 禮記 禮運
if you've some knowledge of confucianism, you can find components of 五倫 from these eight verses:
each one of these have two "人義"; so five ...
An Idiom puzzle should looks like this
1.continuously non-stop like river
2.one column supports the sky
3.full of natural resources
5.gain without working for it
一. a column that withstands strong river flow
二. having a skill
三. mature age
四. the end of time
五. needs from time to time
Looks like it should be 瓜瓣瓢.
瓜瓣瓢 probably means a 瓢 made from 瓜瓣. In contrast, 瓜辨 is not a word (AFAIK).
See a printed version of 清・金士松《喬羽書巢詩集》 (https://ctext.org/library.pl?if=en&file=105725&page=51). Since your screenshot looks like it's from a handwritten version of 《御製詩四集》, I suspect that it's a handwriting error. Well, printing is less likely ...