[Q] help, tips and assistance needed.. topic

Hi there xda.!
Thanks for directing me here.
Btw, im using a phone with these specs:
Starmobile Navi Specs

Android 4.2 Jelly Bean
4-inch display with WVGA resolution
1.2GHz quad-core Broadcom BCM23550 processor
VideoCore IV GPU
1GB RAM
4GB internal storage
microSD support up to 32GB
5-megapixel main camera, with autofocus and LED flash
0.3-megapixel (VGA) front camera
Wi-Fi
3G, HSPA+
Bluetooth
GLONASS
1500mAh battery

But i flash a rom to it, micromax a0910 idk if its thw right model.
Now the phone show that it only have 512mb ram instead of it actual ram which is 1gb. Is there a way to fix this? Or should i change back my rom/firmware? Can i have a list of the roms that are comoatible with my device? Is it possible to use the rom of another starmobile navi as my own rom? How?

Thanks!!