Sid2020

You would need to strip down the unit and find the component number and use a company like RS components to try to source a replacement. Another option would be a AliExpress handle with camera and either use complete unit or strip down for parts. 
 

I believe that a new module is required for front camera as it’s part of the 360 system that would add mirror cameras also, never came across a Audi with the wiring in place for this that doesn’t have cameras factory fitted, rear camera can be installed without any new module though 

Never came across a aftermarket airbag and never want to either, will be Audi or eBay for it I’d say

Turbo lag when is when your turbo is not spooling up at the desired rate due to a lack of exhaust gas to spin the exhaust turbine, typically being in a gear to high and planting the accelerator will produce turbo lag until the revs pick up enough to produce more exhaust gas to spin the turbo to provide the boost required. Your turbo will be spinning as soon as you start your engine due to the above reason and will increase in speed with more revs. 

I’ve had the exact same experience with my wife’s Audi mmi as you are having, I ended up giving up and just use CarPlay for everything when I use it. Thought it was just me but even my teenagers moan about how bad the mmi is to use compared to the bmw idrive. Sorry I can’t give any help to solve your problem 

I coded this in but using a totally different method to both you have mentioned, I had to code in lane assist first to get my high beam assist to work. Hope that helps