Not exactly

If you check the pricing page at: https://www.odoo.com/pricing-plan

You could see that you will be charged by every user you create in the Odoo database I mean per database

So multiple Odoo Installations means multiple databases with multiple users

If you wanna calculate the total you will need to pay just sum the number of all users in all databases you will be creating

Hi,

Yes if you purchase an app from odoo app store, you can use it in your multiple odoo instances.

Thanks