The Update brings your LG H345 to software version H34510i. It is not the Android 6.0 Update. It is still a Android Lollipop update with fixes and security patch.
If you bricked your LG H345, you can download the stock kdz firmware from below link and use LG UP to unbrick your phone.
Download T-mobile LG H345 kdz firmware H34510i
Model: LG H345
File size: 1.1G
You may need to install LG UP to flash this kdz firmware onto your LG H345. You also need to install latest LG USB drivers, LG H345 DLL for LG UP.
If you experience “uknown model” issues with the LG UP, YOU need to put your LG H345 into download mode and run the LG UP again;
THe LG H345 DLL for LG UP is essential for the LG UP to find your Phone., We will share with you a guide on how to flash the h345 firmware with LG UP and LG H345 DLL for the LG UP later.