Will windows 11 support all 7th gen CPUs

"But the Microsoft support team told that they will add 7th gen CPUs before Oct 5th."

Could you point us to a document (or other source) in which Microsoft said that? If Microsoft announced -- anywhere -- that Microsoft "will add 7th gen CPUs before Oct 5th", it would be welcome news -- and important enough to be widely reported in the trade media -- but there has been nothing reported in the media or (to my knowledge) in Microsoft documents concerning Windows 11. 

"There are still updates coming in the following days. Means they are really making additions to the list?"

Windows 11 issued Build 22000.176 to the Release Preview Channel a few days ago.  The Build is almost certainly RTM or close to it, and updates between Build 22000.176 and the release Build are likely to be minor.

Anything is possible with Microsoft, I suppose, but Microsoft has been notifying Windows Insiders with 7th Gen processors (e.g. my Dell Latitude 7280 with an i5-7300U processor) that we should revert to Windows 10.  Your guess is as good as mine, but it doesn't look like 7th Gen processors will be supported by October 5th.   I would like to be wrong about that, but I don't see any indication at all that Microsoft is going to support 7th Gen processors by October 5.  A year down the road, who knows?