What's the difference btw the Dev Edition and Enterprise Edition. From sypron's website, I got to know that only Server engine is limited to 1 and user connection is limited to 10. Does it mean I can create only one server instance?
What do you mean by instance? You can create as many ASE databases as you like. And you could install ASE to different directories and then run different copies of the binary (if you say had a multi-CPU server you were running this on).
Remember that the developer's edition is for non-production work only. What are you trying to do with it?