How to change the OS of SKK mobile (cheap china phone)

A

AC Question

I have an SKK Rush Play android phone. I just found out recently that its a crappy, chinese phone and the android written on the box says its already updated to android lollipop 5.1 but it still operates on a 2.3.5 android OS (don't know if Im saying the right things, I have no idea about technology and roms and stuff) I just want to update the OS so badly since I can't afford a new phone. I can't also find the right recovery mode and the right cyanogenmod for my phone but I managed to root it with Iroot. Here's the info of the phone.

Android 2.3.5 (Upgradeable up to 5.1)
1.0 GHz processor
CPU frequency 400.0~1000.0 MHz
Baseband version S6819PXXAME2
Kernel version 2.6.35.7
Software version S12_dhd_x01_047_GSL_HSD_FT_256M_V06
IMEI 353189073628517

also this phone doesn't have a developer's something (Sorry I forgot) and this ****** doesnt have those recovery modes or anything. I also just found out recently that the original SKK mobile in Shenzen China does not recognize SKK mobile Philippines

I would really appreciate the help :)