One Cart Several Stores

i´m going to create a virtual commercial center, wich will have about 40 stores, and i have some questions:
1.- The stores should have their own subdomain so is it possible with perhaps hikamarket and jms multisite to have an unique cart?
2.- Unique registry, one user for all the stores?
3.- Should all the hikashop be in one database or can it be in several?
4.- If i dont want one unique cart, can all the stores have their own cart?

Hi,

HikaShop and JMS have an integration, so with HikaShop and JMS you can have a unique cart for many subdomains.
All the stores will be stored in one database, but you can have restrictions on categories.

Some categories can be seen by all the stores, and others by only one, or some shops, etc.
With HikaMarket, all the stores can have their own cart or use the global cart.

The users will all be stored in one database, so one registration for many shops.

So if i dont understand it wrong i can have the same options with hikamarket and JMS.
But if i want to have different templates for each shop i should use JMS.
And if i want different databases it should be jomres too.
if i want Hikamarket i will only have one database but i can choose between one cart or multiple. And templates?