If you're laid off can you still claim your pension before the lay off time or only after?

If you got three different answers from HR you can expect 10 different answers here. You should read your pension agreement. If the pension is vested, it is yours no matter what you do; if it is not vested, you may not be able to claim it at all, or you may be able to claim the portion that you contributed, which typically vests immediately. If HR does not know the answer, yo may want to consult with the company's legal counsel or ask your own lawyer to interpret the rules for you.