different information about variant

[nullspirit]

I have a lg g4 and shows that its a T-Mobile variant and the model is H81121z on "about phone" but when I put the imei on www.imei.info it shows that its a Sprint variant and the model is LS991. I have a terrible battery life and want to install another rom for well battery back up but without the original variant information I can't do so.
so, Dear folks of xda
what are my options now?
thanka in advance

 

[nullspirit]

this one from imei.info

 

[nullspirit]

that's from about phone

 

[nullspirit]

that's the information on the mainboard