As the title says, among the eight extracurricular credits there is a required 2‑credit winter/summer social practice. Will not participating block graduation?
I indeed have no time because I have to intern during the winter break, and it doesn’t seem very meaningful.
(I asked senior students; some said it would be considered, some said it wouldn’t 
)
Never heard of a card. Nothing has happened, and there are also reports of a several‑thousand‑character report (directly from the person). However, I have heard indirectly that someone, after doing it but failing, cried to the Student Affairs Office and was politely told that there would be no card.
It is not advisable to take risks. The other six credits don’t matter.
This is generally required; if you end up not doing it, you can ask the counselor, who might assign you to a lower-grade team.
Check the academy and the counselor; so far I haven’t heard of any case of not receiving the certificate.
But if you have time, it’s best to brush up a bit; it’s better than facing all sorts of troubles and dissatisfaction at graduation.