I understand that Intel XDK has been retired and the download links are no longer working.
I want to download and use Intel XDK (version 3987) for Mac. Because, I need to update a few apps made through Intel XDK.
Can someone tell me from where I can download Intel XDK (version 3987) or a DropBox link?
Sorry, but those downloads are no longer available. Even if you do find someone who has saved away an installer, it is unlikely to work well without the XDK backend services, which have also been retired.
Please see Alternatives to Using the Intel® XDK to Develop Mobile Apps on the Intel site for help.
Note that the Intel XDK was an assembly of most of the tools described in that article. So those tools are your best place to start. Also, see the additional reference links at the bottom of that article.