I donāt see the point in dramatic topics like these.
Is the FP2 perfect? No, of course not, but no (smart)phone is.
Either you like the phone with all its good, neutral, and bad sides and you keep it, or the negatives outweigh the positives and you send it back.
If you keep your device, and you have issues, you need work with CS or with unofficial channels (like this one) on getting those fixed. But there are already topics existing for many if not all the issues you mentioned.
Of your list, I can say:
[quote]_screen is flickering[/quote]Fixed with software update for me.
[quote]_bluetooth audio with interruptions with most of my headsets[/quote]Fixed with software update for me.
[quote]_phone not usable during charging with some chargers/cables[/quote]Works perfectly fine with my chargers. I tried about 4.
[quote]_battery drains quickly, phone is getting hot[/quote]Use 2G and 4G, WiFi, and yes when you are writing a lot of data (e.g. software updates) the battery is drained a lot. There is also some software like OS Monitor which you can use to check what software is running on the background. I for example use a smartwatch, and this costs me hands down 10%+ of my phone battery. On my old phone the problem improved when updating from Androind 5.0 to Android 6.0, but the FP2 runs on Android 5.1 and this version does not have the battery issues Android 5.0 has.
[quote]_handsfree speaker was not usable (ok since 1.2.8)[/quote]Yeah, its OK since 1.2.8. Look if something is fixed in the latest software update, donāt bother mentioning it. Every phone gets reliability and security fixes, every Windows version needs them as well. Its rather nonconstructive to keep mentioning problems which are fixed. You should run the latest version.