Cadence Orcad 16.3 33 BETTER

I design my schematic and PCB with orcad 10.3 but I have a problem . I updated Windows from Windows 7 to Windows 10. When I try open cadence it takes a lot of time. I mean it opens too late. Also when I open cadence, CPU is overloaded at %90-95.

cadence orcad 16.3 33

I had done projects in the higher version of 16.6 latest hot fix.But my colleague's PC they using Cadence 16.3. But i want to open files from the higher( 16.6) board in lower version (16.3) of board files is possible or not?

I'm new to four layer pcb design. I have designed two layer PCBs using orcad 16.6. So i'm somewhat familiar with orcad tools. But i'm going to design a circuit which includes ECG filter, USB lines, accelerometer etc. So i think its better to use 4 layer board than 2 layer for better performance. The controller used is having BGA package having pin spacing around 0.5mm and diameter of each pin is 0.3mm. I haven't designed a board that includes a microcontroller having BGA package before. Please tell me how to make its footprint and how to route it. I use USB data lines so differential routing must be employed. Please explain more details of differential routing. Also share the steps involved in multi layer pcb design. Any help would be appreciated.(i'm using cadence 16.6 for pcb design)