Hello olivierw! Thanks for posting and welcome to the Community.
Great questions! The AV18, AV28, and AV35 are all console designations that were used with multiple Lifestyle systems each. If you could provide the top level Lifestyle systems (e.g. Lifestyle 28 Series III) for each and how you would like them configured we might be able to provide some guidance on what will work and what won't. Generally speaking, most of our Lifestyle systems are not capable of being mixed and matched in this manner. Each generation had different capabilities, firmware to make it work, and a variety of speaker packages whose connections are usually not interchangeable.