I'm looking into making a cash reservation and using a Club Upgrade certificate but I've never done this before. I've done my research but most of the information out there is from years ago and some is clearly outdated.

Supposedly you can check for rates online but you have to call to make the actual booking, is that still the case?

Apparently there are two codes that can be checked online: the Z34 rate only allows for the $100 stay credit and the Z38 rate that allows for both Club Level upgrades AND the $100 stay credit, do I have that right?

For the dates I'm interested in, the Z34 rate is only about $10 a night more expensive than the Member Rate but the Z38 rate shows as unavailable, does that mean I'm out of luck? I saw reports from May 2016 that no one could pull up the Z38 rate online anymore, is that still the case? My trip is almost 3 months away and there are still Club Lounge rooms available, so I'd be surprised if upgrades can't be used.

Eventually I'll probably have to call either way, I just wanted to do my homework beforehand.