For life I got you. It’s used mainly in text to say I got you but for life it’s pretty self explanatory if you look at this definition and if you don’t get it let me explain it for you kindergarteners.
If someone texts/says flgotchu it means they have your back for life.

n. The birth name of somebody who has changed their name. Most commonly attributed to trans people, but can be attributed to any person who has changed their name. (sometimes written as two words: dead name)

v. 1. To call somebody by their deadname.
v. 2. To out somebody's deadname to the public.