There are no such "benefits" to stay on Diners network and it's better to switch to Visa platform unless you are okay with frequent card declines for offline txns
Depends on the POS machine/payment gateway. Most of the new ones (the touchscreen ones) work fine. The ones from HDFC bank generally work too. Others are a hit or a miss.
If the machine accepts RuPay, it'll accept Diners Club too.