Can a cross-platform app do the following or will i need native apps

Alright So after months sitting on my asss i've decided to take action and develop an app for other sales consultants in my industry.
The app i have in mind is quite basic, it need to feature two types of financial calculators and be able to pull data (prices/quotes) from a server thats updated every 2 or 3 days. It'll llso subscription based.

I wanted to know if cross-platform tools like PhoneGap, Titanium could do the following:
1) obviously work on all major platforms like iOS, andriod, blackbery & web.
2) work without an internet connection for mobile devices (essentially i'd like to allow calculation formulas and data to be stored on the device until the consultant decides to retrieve updated quotes over wifi or 3g - and without going into the AppStore to update)
3) Is it possible to prevent consultants from sharing their login details with other non-paying consultants. For example limiting to 3-4 IPs per account?

Im planning on outsourcing this so I just need to know the right questions to ask.

Thanks for your help!