Can I update to ios8 on a first generation iPad

I would contact Apple care. it might not be compatible with th new OS

Hey dude, you need to check your icloud account and be sure of your password is correct so that you can update and can download at the appstor.
you need to go the settings and below you can see the account sync, you to sign in or to create an account on icloud

Try recording using the voice memo to check the mic if you can then mic is working if not then either downgrade your ipsw to the previous firmware if you are sure it stopped working right after the software upgrade or replace the mic

go to app store and find out then download

I am assuming you have tried the Apple standard action of removing the Facebook app completely and then reinstall?

That's because it's simply not powerful enough to handle ios8. I know apple gave the update but unless they give a new bug fixing update to fix the crashing, your stuck with ios8 and a crashing iPad.
I have my iPad 2 with ios7 and I'm not planning to update it.

Yes! Plug into PC and sign in to iTunes account!

You might need to update the Bejeweled app. Go to the App Store on your iPad and download any app updates.

If you updated to IOS8.1 then it's got a glitch in it.
You need to go back to your last restore (if you saved it) or update but to IOS8 (Not IOS8.01)

This article should have everything you need.
How to downgrade iOS 8 to iOS 7 1 2