Hi
You have described two different issues.
Restrictions
The Restrictions passcode cannot be bypassed, nor can it be recovered other than by the person who set it either remembering it or referring to where they noted it down. The iPad would otherwise need to be set up as a new device in order to remove the restrictions. However, that is not your main issue.
If Restrictions is still enabled, then the iPad was not erased ready for you, as the new owner, to set it up for yourself. From what you have described, it seems that the iPad still has Activation Locked enabled.
Activation Lock
Activation Lock can only removed by the previous owner - either by them entering their Apple ID and password on the device or by them removing the iPad from their devices list in Find My iPhone via iCloud.com.
If you cannot arrange for either of these steps to be taken, then you will be unable to use the iPad as your own. There is no way around this security feature.
If the previous owner cannot recall their Apple ID email or Apple ID password, they should follow the instructions here:
If they still cannot recover this information and remove Activation Lock, ask them (as the previous owner, not you as the new owner) to either contact Apple Support for assistance or to accompany you and the device to a Genius Bar appointment at Apple Retail Store, taking their original proof of purchase with them. Country-specific telephone numbers for Apple Support are available here:
Contact Apple for support and service - Apple Support
More information and instructions:
Turn off Find My iPhone Activation Lock - Apple Support
