The middle picture of the seedling looks like plumeria. It is known as mildly toxic:
This widespread plant is mildly poisonous, ingesting leaves or flowers can irritate the digestive tract. Itâ€™s the sap thatâ€™s irritating and a few people develop rashes when they get it on their hands from breaking a branch or leaves.
https://great-hikes.com/blog/poisonous-p ... -paradise/
Is the bottom picture the same plant? Plumeria doesn't fruit:
The plumeria tree blooms in the summer and features waxy, showy flowers consisting of five petals in a funnel shape. When the flowers begin to wither, they are replaced by long, slender fruit. A nonedible seedpod, the plumeria fruit reaches lengths of between 6 to 12 inches and features a dry, brittle covering. The brown seedpods do not attract any wildlife
A somewhat similar appearing tropical plant is frangipani, but it also doesn't fruit.
frangipani seed pod showing seeds