[Q] need help in Samsung-b5512

hi everbody
i'm new to android systems, recently i bought a NEW Samsung Galaxy Y pro duos (B5512) smartphone :

gsmarena.com/samsung_galaxy_y_pro_duos_b5512-4371.php

it has android ver. 2.3.6 pre-installed , 2 cams , touchscreen & QWERTY keypad , i'm wondering if any one can help me with some issues:
1- can it be upgraded to the new version of android ISC 4.1.1 or 4.1.2
2- when making calls the screen dims and go to sleep even if i put it in speaker mode and not close to my face for the sensor to work so i have to press the power button to activate the screen and end calls
3- in standby mode pressing any key activates Google search feature , I need to replace it with the dialing number function like nokia asha
4- i make/end calls with the key pad but receive/reject calls only with the touch screen by sliding a circle , which is not good in many times , can i customize a key to answer/reject incoming calls instead/beside the touchscreen

I'm a system administrator & I think I can do hard procedures if guide write

please note that I need not to void the warranty

many thanks in advance, any help will be appreciated.