I’m assuming you are talking/asking about Parc de Princes stadium, the traditional home stadium for PSG? I am following your post, as I will be attending the Parc de Princes for a few of the Olympics soccer matches next summer, and want to learn more about the venue, etc., before actually attending the matches there.
As of today, I have very limited info for you, as 1/ I haven’t attended a PSG match and 2/ I haven’t been inside Parc de Princes stadium yet. That said, I am in Paris, and just realized the Pro Beach Volleyball Tour arrived in Paris today at Roland Garros - right next to Parc de Princes - for the Olympics qualifiers, and I almost certainly will be going at least once over the next 3 days. When I am at Roland Garros, I am going to try & take a tour of Parc de Princes (inside; they have tours) to get a sense of the stadium, etc. If this would help you at all, e.g., if you have any more questions besides your #3 above, just let me know & I’m happy to try & answer them/get them answered. (You can DM me or just post them here by tomorrow.)
Otherwise, re your questions, I only can offer the following as of today:
1/ Don’t know.
2/ Don’t know, but the Olympics is also using a huge official ticket exchange site (w/ restrictions to only use same, as Parc des Princes), and my guess - pure guess - is you could unload your tickets on the official site pretty much at the last minute, given the overwhelming popularity of PSG here. Re the weather, yes, Feb very likely will be cold & wet here, but looking at the plans of the Stadium, it looks like there are two giant overhangs, and you could simply choose tickets that are well under that overhang. Getting to the stadium even in snow should be no problem, as the Metro here is really, really good.
3/ Using the 3-D vision on the Pard des Princes/PSG website when you choose upstairs tickets/seats under that overhang, it seems they should be good, but this is something hopefully I can really answer if I can get in for that stadium tour.
4/ Not sure, other than the stadium is on the edge of the 16th arrondissement, & the 16th is a nice-to-quite-nice area, so you may be able to reserve a nice dinner you could walk to from the Stadium, to avoid the exit crush in the Metro. I’ve walked around the area a fair amount, but don’t know a restaurant off the top of my head - except, if you don’t do better, the pretty cool newly restored & opened Hotel Molitor has a bistro, and is only I think about a long block or two from Parc des Princes. I’d imagine you could find a pretty good reso somewhere w/in some walking for dinner/drinks to let the crowds leave, depending on how far you’re willing to walk in that weather.