is acceptable between pins 3 and 4 (Vin+ and Vin-) in both directions?
Differential input voltage range is max 250mV. It is OK. But will be destroyed
AD8211 if 30V with inverse polarity is connected?
The max voltage across the inputs of the AD8211 is +-500mV. This is inherent to
the design of the AD8211.
A part like the AD8202 and the AD8206 would be able to handle 30V differential
input in case something goes wrong.
Is this is a concern in the application, then the AD8211 is not recommended
since it will not survive 30V differentially.