Giant TCR Once edition

I found this on auction and am trying to piece together what it is worth.

It clearly is a Giant TCR bike Team ONCE edition, what does the team once thing mean?

It also clearly has aftermarket parts, like the seat, clip in pedals, and whatever those bars are.

I really want to try and compete in a tri this year or next. would this be a good bike to do it on?

What is the max I should pay for it?

Thanks!