Omni and Kioka were released together, I believe.
Liyure was released shortly after, and retired shortly after Omni and Kioka.
First was on the site a week before the eggs retired.
Well, not as Clouding, as like Cutieputootie970532 whatever. xD

I'm pretty sure the Kioka was released at least a couple months before the Omni, actually. I'm sure I saw a blog once that listed their dates, and there were a few months in-between.. You can definitely tell the difference in the art quality, too - both have their flaws but the Omni's are a lot easier to overlook.

After the Liyure came in mid-2008, there was the Aerix that December. The whole retirement thing came in mid(or was it later?)-2009, and it was only with the Ezahni last year that the no-Credit-Creatu thing was broken.

If that last question is concerning the current ones, I'm pretty sure I've seen it said that there will be no more retirement - just wiser management of egg cycles. Like. A big reason the old ones had to be retired was that they weren't worth all that much anymore, because one egg type would stay in the shop for months on end before being switched out. They weren't managed well at all.

The monthly thing works much better and keeps values decent, as do dye kits for the naturals, so retirement isn't as necessary. P:

Oh cool. Yeah, before I took a break from Res, I remember people selling Omnis for 50k. :p Although the economy was much different back then, too. xD Thanks yoshi. ^^