際/さい

Question 1

際(に)

Answer 1

“When A”. Polite form of とき, used for actions or events. Found on newspapers and instructions.

名の　+ 際(に)
辞書形/た形　+ 際(に)

Question 2

に際して　にあたって

Answer 2

“At the time of A (which starts now)”. Polite form. Only used for good things. Used on special times like marriage or opening a store.

名　+　に際して　にあたって
辞書形　+　に際して　にあたって