BGP is included as of IP Base on ISR 4k    Stefan Mansson ISR Group,  Cisco  

Performance should not be an issue. As of 16.7.1 you can unlock the ISR4000 series performance shapers with a Boost license.  With Boost license 4321, 4331 and 4351, all will have a throughput up to 2Gbps+      

You can't open the cover of a 3845.  3845 has a modular motherboard which slides out of the chassis.  The board is mounted on a metal carrier that contains ejector latches to assist with insertion and removal.    Loosen the two screws at each side of...