To start from the last, PR21 is a Project (Gaming with Accelerometer) by Cytron Technologies which is inclusive of accelerometer and a Graphical LCD. You may find a sample source code and other relevant information through this link (
http://www.cytron.com.my/viewProduct.ph ... Ef0ns2t4A=).
About the pins of your GLCD, i would like to know what type of GLCD Driver you're using. If you use TG12864E same as PR21, 2 Pins (Pins 16 and 18) of the GLCD are NC (No connection) which means you only need to connect 18 pins. Check Page 3 for the description (
http://www.cytron.com.my/usr_attachment/PR21_DD.pdf).
If you want to use PR21 sample source code with PIC16F877A, you need to modify it as the project uses PIC18 and yours is PIC16.
Hope this is helpful.
Goodluck....
Ebby.