CupraDine

A quick google of the part number on your cable suggests it's USB but I may be wrong. Are you using this and a USB lead to connect a phone? If it is an iPhone you will need to get the iPhone specific cable, you may find them cheap only but you can always ask your local dealer for the cable. If it is a non iPhone (Samsung etc.) you may find bluetooth audio more difficult. 2013 models support bluetooth streaming it with the full navigation pack I think. Someone else may know more than me on this. If you don't have this then it's either an aux cable or something like the Bovee tune2air

There is a sticky thread here for C6 pre facelift If you search online for the brochures for each generation/facelift, so A6 C6 2009 brochure will get you the C6 facelift version. You can find the brochures with a spec for each trim. Same for the C7 (2011/2014 i think) depending on the generation/facelift you are looking at. Le Mans is pretty well specced but there are still many options to be had, like electric folding mirrors! Le Mans is just S-Line with a few more options like interior lighting package ticked. You may find a well specced SE is better as it has a softer ride to. Both C6 and C7 could be optioned with it. The C6 has a single sensor in the front grille below the plate, the C7 has what look like two turbines where the front fogs usually go.

The suspension control is usually for the active dampers and the allroad setting is just the height of the air suspension. Normally these are greyed out if enabled but not applicable to your car.

That is just the heat shield for the exhaust, you might be able to re fix it with a new clip and a large washer (larger than the clip to go over the whole in the shield). Otherwise you may need a new one if it is very loose, don't use cable ties as they may melt with the heat.

If you have the AMI port in the glove box, try the Bovee Tune2Air AMI or similar. This is expensive but worth the money according to others. I use a cheaper one which does have the odd hiccup and doesn't support the media controls. Search for "bluetooth a2dp ami" or similar to see other alternatives. AMI is the port in the glove box, A2DP is the bluetooth streamning standard. Also your device (phone or whatever you use) will need to support at least 2 bluetooth connections simultaniously (most modern smartphones do).

My suggestion would be to drive both, and see what fits you best. The C6 may have more power, but the gearbox is an older tiptronic and a bit slow. You may find that the C7 is faster with less power because of this.

For the C6, there are 3 power outputs. 225 is the pre facelift first engine 233 is the pre facelift second engine, avalible from 07 on model years I believe. 240 is the post facelift engine, 09 on cars. The C7 uses different, but revised engines from the C6, and thus, different power outputs of 205, 245 and 313. Hope this helps.

The drivers seat belt must always be buckled for the car to be happy, unlike other passenger seats where if it thinks someone it sat in it without one. The sensor for this is in the seat buckle itself, and may just need replacing.

Likely you would need the whole MMI upgrade, screen, center console, multiple control units, along with other module firmware upgrades to support the new hardware. Not an easy job i think. Do you have/can fit an aux port, might be easier to do that and use a mp3 player or bluetooth adapter to get your music

I don't know on the A4, I know the A6 is the C6 generation (2005-2011). I think the B7 generation has a handbrake, and the B8 has the electronic one.

I would look for a petrol based on your mileage. While you are looking at an older car, some of the pre 09 diesel engines have a DPF filter (I think only the 170hp ones) fitted. Meaning longer motorway drives are needed to regen them, otherwise they clog up and cause problems. If you are willing to get a diesel either make sure it does not have a DPF or read up about them and make sure you drive it often/far enough to regen the filter. Removing the DPF is a MOT fail and/or a large fine now unless you have a friendly MOT guy.

I also use a cheap ~£30 bluetooth adapter. Works well and auto connects when I start the car, I would prefer steering wheel controls but I can live without it. I have set my phone to launch Android Auto on connection, which has the voice recognition so I just shout at my phone to change tracks and playlists.

IMO You may find you need other modules etc. coding and firmware updates to get this to work. A specialist would be able to advise further on what is required. If you buy a generic one you will loose functionality outside of a headunit, such as car and air conditioning control if you have that. You can get aftermarket replacment ones for your specific car but these require further research as not all kits are created equal. Do you have/can fit the ami port? It's not too much money to fit and code in usually. From here you can add things for bluetooth music streaming. I just have a bluetooth adapter for music and use the phone screen mounted for everything else, online radio etc. It launches Android Auto (on my phone) on connection as well.

The fuse is located in the boot, behind the panel on the right (you would have removed it to change the outer light if your car is RHD), I believe they are fuses 7(Right) and 9(Left) in the black fuse holder but check your manual. You said the lights didnt come on, which lights? If you mean the side/running lights you will need to switch the lights to side/on (not auto if you have that). Also check if the lights come on when you brake, it is the same LED's but on a different circuit. Again check the indicator, reverse and fog lights, if non work, then it could be the fuse. However, if only your brake/side lights don't work there are a couple of possibilities. Most new lights don't come with the bulb holder, so you may have swapped yours in which involves plugging a molex style connector for the LED's. Check this is not the wrong way round Check the cars computer using a VW/Audi diagnostics tool, it may have stored a fault in the module which has disabled the lights (as mine did when I changed mine). Clear this and try again.

If you are on a budget then obdeleven, but this is more limited than VDCS