Unlimited. JioPhone comes with 4GB Internal Memory - so, you can store as many contacts as you want, depending on the free memory on the phone.
Yes, the JioPhone does have FM radio. In fact, it is wireless FM radio. You do not require to use the earphones to use the fm radio.
Yes, JioPhone does support the Gujarati language.
No. There is no WhatsApp support in JioPhone.
JioPhone comes with 4GB Internal Memory. So, you can save as many as you want - depending upon the free memory on the phone.