today I have three questions at once. Previously, the SuFu didn't help me and thank you for always answering my other questions so super fast and well. really great

So now my three questions:
1) I have the normal concert radio and I want to install a MultiLenkrad. Can I use the old radio with it? So it's the multi from a D2 facelift.
2) I have the normal speakers and I want to install those of Bose, incl. Amplifier, so it's a complete set. Do I have to consider something? Can the old cable be kept in it, so that you only change the boxes, or do I have to pay attention to something important?
3) I still have the "old" automatic selector lever with 4,3,2 although I have the facelift, but at that time everything was Rudi's rest ramp with Audi... now my question, can one simply install a selector lever with S or can it not at all? Because from the pictures I had looked at, it's all the same, from the size and so on. And even if it doesn't belong right in here, if that fits someone has a dial lever to lie around with S? Can write me a PN, too.
Thank you very much for the answers in advance. I know it's a little more this time, but I didn't want to open 3 Threats at once.
Best regards from Berlin
Addi
PS: Is there a meeting of the Berliners here in the forum??