I can have a go at trying to answer this but others will be along with more detailed information I think...
1 - It would depend on if or not they actually do use the same ECU or not. Only way to check is to have a look I think. To be honest the same ECU can also be used on cars with other engines too but obviously the software/maps are completely different.
I would not recommend just downloading a bin from a 170bhp car with the same ECU and just uploading it onto a 140bhp car. This won't work as the software part will also be VERY different as well as the maps.
You COULD however use the 170bhp bin to see which maps are different and as long as the 140 bhp car has similar hardware (turbo, intercooler, rail, injectors, etc) use these maps to get the 140 bhp car to 170bhp. Normally it is not just the ECU map thats different, normally the faster car will also have a bigger intercooler or something too....
I dont know much about VW/Skoda/ETC someone else might be able to add to this.
2 - covered above
3 -
WinOLS - for remapping. Costs a lot of money but can be found for free if your willing to spend some time searching the internet.
ECUSafe - removes the DPF/FAP from a lot of ECU bins. Not sure if it works on the cars you listed but its worth a try.
http://www.ecuedit.com/ecu-safe-t374 - You make your own. Its very hard, have a look around the forums to see... best place to start is get WinOLS, open your bin and try to find some of your maps.
5 - Try using ECU Safe to do this... its quite straight forward. You download your bin, run it through ECU Safe and it gives you a bin with the DPF removed (assuming it works with your car).
6 - On my car (Peugeot) a seperate 'BSI' computer controls all that lot and is interfaced through Peugeots own software (PP2000). I guess audi/vw would be similar, maybe its possible in vagcom but I never tried it...
7 - No idea, looking at the cost of them I would rather pay less for a decent map file, where I can see what changes have been made to my car, and just flash my original file in case of warrenty (also a 2 minute job on most diesel ECUs).
Just remember when reading/writing to the ECU remember two things:
ALWAYS keep a backup safe copy of your ORIGINAL bin just incase you need it one day!
Make sure you write to the ECU with the voltage stable. Most people connect the car battery to a charger or a second battery during the ECU writing procedure.
Also I can't say what software/hardware you need for reading/writing bins without knowing what ECU you have...
bin = the file that you read/write from your ECU