apps are opening automatically & screen becomes yellowish

I would follow this guide to open the phone and inspect the connectors for the LCD and Digitizer.

They may have become partially unseated and misaligned. However, depending on how hard the physical impact was, you may need to straighten out the frame. If you do this, I would recommend you remove the logic board as well so you don't accidentally damage it.

Follow the instructions closely and keep track of your screws and don't force anything or apply sudden movements. Everything inside can be quite delicate and break easily. Come back and post pictures and we can give you more guidance.