Thank you for your advice on the topic!
I'm abroad for less than 3 weeks. I've been reading about it here and it seems that 3-4 weeks would be a maximum, so hopefully that will be ok.
1. That's what I was hoping for, that it won't be noticed. Hard to believe that they will compare the original sent by mail with PR app with the scan, uploaded to visa extension app in that much detail, on the first look they really similar. Yet, once I started to stress about it, the question is raised - what IF it is noticed, and how serious it can get? (That is why I was thinking about even withdrawing PR app, waiting couple of months and re-applying, with all new forms, including this one, or applying outland instead. Because if that can be counted as misrepresentation, or faking the notarial document, even without intention to do so and that all the information provided are truthful, I would rather wait for couple of months more, even 1 year or so, than have 5 years ban)
2. I will follow your advice and withdraw extension app. If I withdraw, do they keep it in the records? Or it's like it was never submitted? Even if they have records, are the chance they they will compare every single detail are smaller? I mean, it was withdrawn after all.