Must accept/reject before hearing back from other schools?

Hi, I received an acceptance email from CSU Northridge.

The email says that I have to accept or decline by January 4th. Although I'm interested in accepting, I'm still waiting to hear back from other schools, which will be in February. Am I able to accept as of now, but potentially change my decision when I hear back from other schools?

If so, does accepting this university notify other universities (perhaps via PTCAS), possibly influencing their decisions?

Thanks!