CX uses the Lotus and the Araliya lounges- wth the former being the designated 'First' class lounge. I'd rate the Serendib lounge to be better.

If your oneworld status number is in the booking, you should get the appropriate lounge invite along with the bp. Ask if UL can check you through- both are on Amadeus (infact UL bookings with my CX ff no in automatically show up in my CX account).

CX checkin desks open just under 3hrs before the flight (I've had to wait 'pre'checkin area for the counters to open- security doesn't let you in to the check in hall).

The process described by moa999 still works for transfers (at least did as of 2 months ago) though I'm not sure if you will get the CX bp more than 3h before the flight. (UL handles ground handling for CX, and most of the check-in staff are UL employees in CX garb)