In accessible Arduino pins after connecting RA8875 display shield

Hellow All,

I have posted a query: https://forum.arduino.cc/index.php?topic=708056.new#new under Forums-Storage. Did not get advise for my query. May be I have posted in wrong discussion forum. Thats the reason I am posting it here again. Sorry for re-posting.

I have good experience in C++ coding and recently started learning Arduino programming and new to Electronics. Started to work on a personal project for a Point Of Sale(POS) terminal machine. Purchased Arduino-due. Ordered and received a 7 inch capacitive touch TFT display from: https://www.buydisplay.com/serial-spi-arduino-7-inch-tft-lcd-touch-shield-ra8875-for-mega-due-uno.

On looking the display catalog from buydisplay.com, I decided to go for this display as I noticed there was a SD card slot thinking it will be usefull for storing the billing details so that a detailed report can be generated later based on items and date of purchase.

My requirement is as follows:

  1. A TFT touch display for inputting Item and quantity.
  2. A calculator billing program in Arduino-due to calculate the total Money for the purchase.
  3. A thermal printer to print Bill.

I started to code the screens by editing capacitative touch samples from buydisplay.com.
Following are the issues I currently encounter:

  1. Arduino - Due do not have RTC.
  2. Storing data to SD card present in the display-shield from buydisplay.com(RA8875 shield)- Samples to load and display BMP image provided in buydisplay.com compiles and uploads successfully in arduino. But the screen is blank. Hope accessing SD card slot is not supported from the purchased display.

I think connecting Data logger module will solve RTC and data storage issue. The real problem I face is: After connecting the TFT display shield to Arduino- Due, the pins from arduino are not available further to use as the display shield hides it.

I am looking for the following:
=>How to utilize the Arduino - DUE pins that are hidden under the display shield for connecting thermal printer and data logger shield. Can any one help on this please......

Thanks in advance.