I have a multiple l-entry Schengen C visa obtained on the basis of my sponsor friend in Poland. When I applied for a visa Isubmitted an itinerary for 29 September to 8 October, and the embassy granted me a 70-daysm multiple-entry visa, even though I asked for only 9 days. So my questions are:
Can I change the date of my flight as I am getting a cheaper fare if I travel 4 days after my intended travel?
Can I do another trip say in November on this same visa, or I will have to show some other proof at the border upon entry?
Can I go to Germany for a few days from Poland if I want without any checks?
Just to be clear I want to have a good record for my future Schengen visa applications. I don't want to break any rules whatsoever.