My understand is if I already have a MDK version, then I just need to apply an MDK-Community license.
But it looks like the license I requested only an MDK- ARM basic license and has 256K code size limitation.
The MDK version what I am using is V5.26.2.0. I am thinking should I download a special version of MDK specially for community?
The procedure for an MDK community license has changed:
https://www.keil.arm.com/mdk-community/
This would require a recent MDK version. 5.26 is very old, the current version is 5.39, which you can download from the above.
You may also be interested in the brand new MDK6, which uses VS Code as its IDE:
https://community.arm.com/arm-community-blogs/b/tools-software-ides-blog/posts/mdk-v6-released