I am developing an ios app. Till now i followed adhoc distribution using testflight for distributing builds to clients. This process creating so many problems like making the builds ever time if i recieves the Device UDID .So I want to submit it to app review process. to go to app review process i have a few query about that

We are developing this app for a company which is not located in Volume purchase program countries.so we can't distribute via B2B. In future we might give the same app to various clients also. so my queries are 

1. The app has login id and password is there. so everyone can't use this . will apple accepts this app . if so ,should i do anything for that. if not so, what would i do to make it available in app store.

2.In future the app customer base might grow. so if i submit different app with the same app content will apple accepts this. if not, should i do anything in first submission.

3.Is apple mentioned any where about the userbase of app.

Any Help would be appreciated.

Thanks