Hello @Apurva Kombde ,
Welcome to Microsoft Q&A forum.
Are you using a web installer(Visual Studio Professional 2012)?
As only the DVD/ISO version of Visual Studio Professional 2012 is available(Downloads & Keys - Visual Studio Subscriptions), you may get the errors about downloading packages from the internet while installing VS Professional 2012.
Please try to download the complete DVD version of Visual Studio Professional 2012 and then install it.
BTW, some old/EOL versions of Visual Studio are only available for paid level subscriptions. Try to sign in above website with your paid level subscription and then you should see the available download link for VS Professional 2012(DVD). Download the complete DVD version and then install it.
Kind Regards,
Tianyu
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