Adobe creative suite 5.5 and Windows 11

CS5 is discontinued & unsupported.  It's never been tested on Win11 and never will be.

We can make no guarantees it will work on your system.

You can gamble & try it or just hold on to Win10 until you're ready to replace with modern software.

MODERN OPTIONS:
Photoshop Elements or Premier Elements (approx USD $100, no subscription needed).
https://www.adobe.com/products/photoshop-elements.html

Creative Cloud Photography Plan (approx $10/month for 12 months). Includes the following:

• Photoshop CC and Photoshop on iPad
• Camera Raw
• Lightroom on desktop, mobile and the web
• Lightroom Classic
• Portfolio website + hosting
• Adobe Express (free starter plan)
• Bridge
• 20 GB cloud storage (upgradable to 1 TB).

https://www.adobe.com/creativecloud/photography.html

Premium Adobe Express ($10/month).

• Creative Cloud Express app (web and mobile)
• Premiere Rush (desktop and mobile)
• Photoshop Express (mobile)
• Spark Video (mobile)
• Spark Page (mobile)
• Adobe Portfolio + hosting
• 100 GB of cloud storage
• All premium templates and design assets including the entire collection of over 160 million royalty-free Adobe Stock photo collection.

https://helpx.adobe.com/express/using/express-overview.html

Creative Cloud All Apps (51 + apps & services) and Single Apps Plans
https://www.adobe.com/creativecloud/plans.html

yes, but it may not be easy.  a number of people have posted about recent problems activating their cs5 and cs6 programs.  cs5.5 is going to have the same issues which don't really seem related some much to the programs themselves, but users use of older os'es with browsers not having tls 1.2 support.  that shouldn't be an issue for a win 11 user.

of course, you'll need a valid serial number (6 groups of 4 numbers) to activate, and you may need to use compatibility mode to install, but compatibility mode has a part of windows (including win 11) for a long time.  Run Older Programs in Compatibility Mode in Windows 11/10 (online-tech-tips.com)