Basic questions about creating a vertical crm

I'm brand new to this and have a few questions:

I want to use the vertical i am building for myself to test it and use it in my day to day, so i can refine it. If the app is not published is this possible outside of a sandbox which would no be ideal for live data?
After I publish a vertical, can i use my own app with my zoho one account for free?
What if i want my vertical to have tie-ins to other apps from the app store? For example for sms triggers, zoho doesn't seem to natively support sms/mms. So i have to use a third party connector from marketplace.
What about tie-ins to other zoho apps like campaigns?
Can i set a different pricing structure for different user levels? IE a user in a company/group with global access to all records would have different price than a user with limited access to only their own records?