There is no official dedicated Facebook Messenger app for Windows Phone 7.x; They chose to only support 8.0 (and later). There is an official Facebook app though, which does work on Windows Phone 7.5 and later.
If I remember correctly, you can also still use Facebook chat via the built in Facebook integration via your "Me" tile (also in the address book), ...
Windows Phone 7.x doesn't have inbuilt support for screen capture. However if you have a phone that is (a) developer unlocked and (b) interop-unlocked there’s an app you can use for taking screen shots on your device. The app is called Screen Capturer
No, it is not possible to use the phone's Micro-USB with an Ethernet cable for internet access. Even with a USB Ethernet adapter, the phone doesn't have the driver support.
Try a WiFi router or a SIM card with a data connection to avail of internet access without turning on your PC.
From Windows Phone Help:
Alarm volume is separate from the overall phone volume and can't be
changed. As long as your phone is on, your alarms will still ring out
nice and loud even if you turn down or silence the phone volume.
The above applies to any Windows Phone out there. I used to have an LG Optimus too and I can't remember being allowed to set ...
The easiest way to download apps for 7.8 is to use the Marketplace app that's already on the phone. All of the apps in there will work on your phone. Most new apps that are being made for windows phones will only work on the Windows 8 phones. As for Facebook though you don't need the app for that because it's built into the phone, you can just go the ...
All the contacts on Windows Phones are synchronised with online services, or stored on the SIM card, so all you should need to do is to set your new phone to synchronise with the same online services, and transfer the SIM across (if you use contacts stored on the SIM).
If you really did want to export as VCard or CSV, your options are limited as on Windows ...
If there is sufficient charge in the battery to run it, the 3 finger force reboot should start it. Hold down the power button, camera button, & volumn down all at the same time for about 10 seconds and you should feel the haptic vibe that it is powering up. Let go of all buttons when you feel that vibe and is will boot up.
Looks like you want to revert back to 7.5 instead of reset settings.
Since it is an update ant a setting I think the only way to revert back is going to Zune and revert to backup it did when you install the update.