No
You cannot delete a profile on Minecraft at the moment.
Minecraft is all about the account you made, you can log into that account on any computer, you are not forced to play it only on the computer that you purchased it on.
Simply download the new minecraft laucher from either minecraft.net or mojang.com and it should automatically load up a default "profile" which is the newest version of minecraft.
First of all, if you haven't already, you need to purchase the full version of Minecraft to access skins. There are many sources of Minecraft skins all over the internet where you can download skins from. Do an Internet search for a skin of your liking and download it to your computer. Once you have done that, log into the official Minecraft website with your account, go to your profile and upload a skin there. See the related links for a couple of Minecraft skin databases.
Google a Minecraft skin website, like the skindex, and then you can browse the different skins in it, and download one that pleases you. Then, you go on minecraft.net and go to your profile, and upload your skin.
If you use MultiMC you can have multiple copies of Minecraft installed on one computer, with different versions and mods.
No, Minecraft shouldn't harm your computer, that is if you have a good computer with good FPS if not then minecraft will run slow. In other words you may have gotten it from a different website which may have a virus or in worst cases harm your computer. Make sure to download it from minecraft.net for no virus which could harm your computer.
you can either migrate it or not its up to You.
Minecraft doesn't mess up your computer. Minecraft is a malware free program.
no you can not
No you cannot change your minecraft email account, but it is possible to change your screen name by loging in to minecraft.net with a different computer...