Attention!!!: This solution may only be interesting for players who want to finish both, the Windows Phone and the Windows 8 version of the game.
There is a nice trick to complete this game twice, by only playing it once on either device. But I advise you to play it on the PC/Tablet because of the handling and maybe if you are making use of it, for the time glitch.
Here is how it works:
Just start a new game on your Windows Phone and play the tutorial. At a certain point you can manually save to the cloud through the options window. After that you can start the game on your PC/Tablet and repeat this process until you can save there. At some point the game on PC/Tablet will ask you to load the game from your current device or load from the cloud. Choose to load from the cloud.
Now you normally can play through the game until it comes to the point were you are about to unlock an achievement. At this point you have to save your game manually to the cloud BEFORE you unlock any achievement. Then start the game on your Windows Phone. There you can do whatever is required for the achievement and unlock it. At the point you see your achievement unlocking at the top of the screen, click on the home button and return to your phones main menu. Close the game via the back button. Now check on xbox.com or on TA or whatever source if the achievement really got unlocked on your gamertag. If it does you now can start the game again on your PC/Tablet and when it asks you to load a save, choose the one from the cloud. You should be on the point before unlocking your achievement. Just repeat the requirements for the achievement. Now you should have your achievement on both devices. If an achievement is not unlocking for somewhat reason (it's known that sometimes achievements can get glitched), then just quit out of your game and load the save from the cloud on the next start until it make's the plopp again^^
There are some achievements were you should take care of because they are unlocking during normal play:
One Step, One Footprint - Raise the population to 150.
Good Luck Follows You - Win 50 one-on-one battles.
Demon - Successfully invade friends' kingdoms 100 times.
Demon's Nightmare - Successfully resist invasion 100 times.
For this four achievements I advise you to look into your achievement stats every here and now to avoid unlocking them to early on one device.
This is only because of the saving of the game. Everytime you load your local save it overwrites your cloud save, so really pay attention on choosing the right save and save at the right time.
I found out this nice trick because I started the game on my Windows Phone a little later and thought about Galactic Reign, which works the same way and I only wanted to let you all know that this cheap trick also works with Kingdom & Lords. And I searched for this info everywere on the web and different forums and didn't found any proof that this works, but it works hundred percent.
If you have any question on this trick, then feel free to ask me and also if you think this isn't a really guide for any of the particular achievements I posted this guide on, please don't give me a negative feedback! I only posted this guide on every achievement, so that you really get noticed about this trick!!!
Thank you for your patience and have a nice day :)