1. It is not a Bianchi but a origin Puch build.
2. Sticker says Columbus SL not SLX. Puch usually marked their bikes accordingly.
3. I would say it is a mid to late 80ies bike.
4. Ther were different Mistral models such as a SLE model coming with different setups.
5. The better versions came with Campy Super record cheaper ones also with Shimano 600. Real low line models also had Sachs Huret gruppos and lesser weinmann brakes. For this particular frame I would go for campy.
6. I will check a original catalogue I have and will get backt to this. Meanwhile look at a catalogue here:
http://http://bulgier.net/pics/bike/...81(in_German)/
This will show that your bike is after 81. The spec sheets will give you a pretty exact picture how they were kitted.