Orientation and pre placement talk

Hello!

I had a doubt if attending for orientation and pre placement talk is mandatory.I read it on the website that it is mandatory for shortlisted candidates.

Also what is the consequence for not attending them?

Like for orientation - does the institute disqualify us for the interview if we dont attend it?

For Pre Placement Talk - Do the companies have an impression on those who did not attend and ask about it in the interview?