I've tried a couple of games and this one seems hackable when you play alone

http://www.omgpop.com/#/arcade/gamelobby/blockles

You can edit the score when you do scan all (bytes to double) and ends up with 3-4 results.

Is there anyway to make the achievements worth more xp? Or really any way to hack XP on this site so that you can level up faster ?

The only way is to hack the games themselves to make getting achievements/winning games easier.