Default [Q] Help with Sprint version in Mexico

First, excuse my poor english.
Ok, i recently buy this phone, and im happy, even when i cant connect to 3g with TELCEL in my country, just EDGE. So, my first question is, is possible get 3g in my country? Cause i try in the *#*#4636#*#* menu, testing CDMA, WCDMA, and others but, when i dont get NONE signal, i just get EDGE.
And the rom in the phone is 4.4.2
The sprint version.
So, recently i discover that has installed TWRP touch recovery. So, i think i can install any rom that i want, but, my doubt is, if i install any other ROM, a CUSTOM ROM, my phone still work with TELCEL in Mexico?
Thanks in advance. Im a member since a lot of time, but i always find answers to what i want already in the forum, but in this case, i dont find what i want. So, i hope someone can help me.