Gratz! I have the same exact phone, a white 1520.
For your questions:
1- Here are my frequently used Apps and Games
Adobe Reader - pdfs n stuff
Air Hockey Speed - good air hockey fun with a friend
Asphalt 8 - if you want arcade driving with amazing graphics, this where you go
Audio Stop Free - music controls show up in the volume controls even when you paused the music, if you want them to go away, use this
Bingo - if you like bingo
CamScanner - take pix of documents and OCR them to get the text
Daily Explosm - if you are a fan of the Cyanide and Happiness series, get this
Dungeon Hunter 4 - high quality top-down RPG, very good fun with MOGA controller
Flashlight - you can guess
Fresh Paint - yes I draw using a stylus X)
Hill Climb Racing - my most played game so far, 2D hill climbing game with "almost" realistic physics
Hot Rod Racers - a 3D drag racing game, good fun
Instagram BETA - official insta client
Manga Blaze - if you read manga
Metrotube - great YouTube client
Microsoft Solitaire Collection - its solitaire
Minion Rush - you should know this if you don't live under a rock

Modern Combat 4 - Gameloft's CoD
MoliPlayer Pro - get this to get the best out of your big screen HD goodness
Pemium Pool - simple pool game, very good
Reaper - artistic 2D hackn-n-slash/RPG
Skype - skype
Skyscanner - air tickets and such
Spartan Runner - best Halo-themed 2D infinite runner out there
Speedtest.net - app for speedtest.net
Star Wars: Tiny Death Star - manager your own Death Star
Steam Center - unofficial steam client (lacks chat option)
TeamViewer - remote access for any your devices running TeamViewer
Translator - it translates stuff bro
UC Browser - chock full of features, can sometimes lag compared to IE
VBA8 - game boy emulator

Vine - vine
Voice Recorder Pro+ - voice recorder
WhatsApp - whatsapp bro
WPCentral - wpcentral app
Windows Phone Insider - latest WP news
WPtrakt - track your tv shows
Xbox Extras - for your Xbox Live Avatar
2. If your'e willing to live with some annoying bugs and slower games (not optimized properly) then go ahead, otherwise I suggest you wait for Lumia Cyan and 8.1's official release.