It does take about 2 hours time to fully charge the JioPhone's 2000 mAh battery.
Yes, JioPhone does support bengali langauge.
JioPhones comes with 4GB Internal Memory - so just like a normal Android smartphone, you can save as many contacts depending on the free space in your phone. In practial sense, you can store unlimited contacts.
Reliance JioPhone does not have call recording function.