go to apps and see whats open??
It's probably just LG's stuffty skin, I use like nothing on mine

idk, I heard you can unlock the bootloader and install roms on an LG, but if you really want to do that do some research
go to settings and look at open apps, remove the apps you don't use and it should run better
thats how I maintain my phone though
my phone is a dumb smartphone so I won't be able to get that ;-;
I sent you an xda thread on how to unlock it, you can probably just install cm and they might update your phone to android L.
The browser issues just chrome, try something else