re installing CS6

According to HOW LONG IS MY DOWNLOAD AVAILABLE at the next link the time is 3 years
-https://helpx.adobe.com/x-productkb/policy-pricing/adobe-stores-online-order-payment-faq.html
For CS6 and earlier you may download ONLY if you bought direct from Adobe via download
-Log-in to your account and click this link https://account.adobe.com/products
--click Order history on the left and then the link to your order that will show on the right
--and finally click the link "Downloads and serial numbers" that will appear
--as always, write the serial number in a text file AND copy that text file and the
---download file(s) to an external drive (or two) to be sure you have what you need
-if you did not buy direct from Adobe via download you must find your original install
--if you have an Education or volume license you MUST use your original media
--the link for an Education or volume license download is not available at all
-if you bought a disc and don't have a drive you will need to buy an external USB drive
-if you bought a download from a 3rd party vendor you will need to contact that vendor

Adobe has removed older version from the public web sites. 

You have to contact Adobe directly for a download link. Have your serial number and details of original purchase available. Make it clear that you doesn't need support for an older product but need a download link. Click the link below and scroll down the page to Individual “Sign in to contact us” It should be possible to start an on-line chat with an Adobe agent. 

https://helpx.adobe.com/support.html