I don't know how to force update. How do you do so because I have a link but from there I don't see a login place, a options button, or a force update button. Do you have to buy minecraft from a certain page for that to work?
To be able to force update you need to have the full version of minecraft and downloaded the launcher then once you have done this you can force update via the launcher . How to force update: Before you log into the launcher press options (above log in) and force update it will then say 'Will force' and at this point you log in. It will then update your .jar.
hope this helps