Yes, most properties will extend Plat benefits if you show your card at check-in. I have done that many times when a non-status friend insists upon making the rez or I do a last-minute join along.

As for status life, although there are many posts conflicting with each other, you should read the terms of the challenge to confirm. It's sounding to me if you only meet the challenge terms then your status is good until the end of Feb the year after the challenge. However, if you were to go on and meet the Plat status requirements, you'd be good for another year (standard term).