I have to give suggestions to my clients about the Minimum Salesforce Edition require to build an app for AppExchange. I had gone through all the editions and had a detailed overview of all of them. I am now stuck between professional and Enterprise edition. I want to know any major kind of differences between them. And Also I want to know about the future of Group edition or any possibility to develop app on it.
The edition they choose does not matter for purposes of development; your application will be created in a Developer Edition org, which is like an Enterprise Edition org but with limited storage space. They should choose whichever edition suits their business practices. For differences, see the marketing material. Enterprise has a lot to do with automation, such as workflow rules, API access, etc.
If they just need to get started, Professional Edition should be sufficient for their purposes. They can always choose to upgrade later. Group Edition has been replaced with Essentials Edition. It is typically not suited for anything more than the smallest of businesses. Again, this has nothing to do with development, so they should make their purchase decision based on their business needs.