Update: UliUdo told me he got the medals without any problems. So maybe there has been an update.
"I believe that both the 10 and 20 medal achievements have been fixed now. I had more than 10 on my PC before starting the game on my phone and the 10 popped immediately or after one game, then as soon as I had 20 on the phone, that one popped too."
I can't confirm or deny this so if it works, great(!), if not or you are still glitched use the method below :).
The achievement is simple, get 10 medals but can glitch on you if you go from 9 to 11 medals without stopping at 10 first. The game won't see it as 10 medals earned and therefore the game will screw you over. Most of the time it will do this if you already have win8 medals.
So if you are like me and your game glitched here is how i fixed it. After I got all my achievements out of the way, including the 20 medals , same glitch is known for this one, i deleted the game from my mobile.
The I installed it again, but before you start the game go in to settings and turn flight mode on or your data connection off. This prefends the game from linking with the cloudsave, and therefore the win8 version. Now you can do it again with everything at 0. After I got my tenth medal the achievement poped.
For it to count go back to settings and turn flight mode off, relaunch the game and let it sync with the cloud, it can take a few seconds but worked like a charm.
I completed these ten they are the easiest in my opnion some of them you can get at the same time.
Castle Crasher
Space Train
The Real Tail End
Dragon Slayer
Well Travelled
Little Wingman
Might Matchmaker
True Expertise
Quick Thinker
Master Scuba Diver
Complete list of challenges from the WP version:
Castle Crasher
-Completed the Castle puzzle without using undo and where your first move is a reshuffle
Space Train
-Complete the Train puzzle using teh Cosmos theme 5 times
Climbing the foodchain
-Complete the following puzzles in sequence: Butterfly, Turtle, Ray, Dragon
All the Right Moves
-Complete 10 puzzles on Hard difficulty without using a reshuffle or undo
Can't Win
-Reach "No More Moves" three games in a row on three different puzzles
The Real Tail End
-Complete the Nautilus puzzle where the last match you make contains a tile from the tail end of the spiral.
Dragon Slayer
-Complete the Dragon puzzle without using a reshuffle or undo
Photo Finish
-Complete a puzzle within 3 turns of using a reshuffle
Go Wild
-Made three consecutive matches with wild tiles
Well Travelled
-Complete a puzzle while using each of four different themes.
Little Wingman
-Made 100 matches
Might Matchmaker
-Make 1,000 matches
You're Basically Cupid
-Make 10,000 matches
True Expertise
-Complete four different puzzles on expert difficulty
Super Speed Runner
-Complete 25 puzzles in under 3 minutes each
Quick Thinker
-Made 5 matches in under 15 seconds
Master Scuba Diver
-Complete one of each of the 4 expert puzzles using the underwater theme
Man of the Hour
-Acquire at least 60 minutes total play time on each difficulty
Wind Waker
-Using the Tranquilty theme, match the following tiles in sequence: N, E, S, W
Pro Landscaper
-Complete the Bramble puzzle 20 times
A shout out to Musquito for giving me the tip to try it in flight mode, and als WinMo Kirby for letting us know you can turn of data connection so you can keep on getting calls :). Thanks for UliUdo that came to me with the knowledge for the update!