Mojang Account and minecraft download.

1. I wanted to change my name on minecraft but i couldnt because i cant remember any of the security questions i was wondering if you could send me a link allowing me to change the questions. Thanks 2. when i tried to download minecraft on my new pc it kept taking to the the page where i have to pick my platform and all and when i done it all it told me i had to buy the game even tho i did about 4 years ago more or less. i would be thankful if you could get back to me as soon as possible thanks .