What are the latest v2 version?
How stable is it?
Where can I find latest ver 2 demo download?
The latest cs-cart v2 version is 2.2.5.
As far as I'm aware only existing license holders of V2 with a valid support contract which covers (perhaps even just covered) the public release date of the specific 2.X.X version can download via their account. Otherwise, you could ask CS-Cart, but I would expect only V3 to be offered to new customers. Existing customers will only be allowed the latest release available as per the upgrades support contract.