if i install the gentech lg classic flip filter will i be able to install your apps and if i install apps before i install the filter will the apps work?

ybb No and no

so with which filter can I use the apps?

how can i just block the browser on a lg classic so that i can still use the app4flips apps?

ybb it says on the apps4flips website.

The website details out everything.
https://www.apps4flip.com/oddsnends/
Look for the paragraph "uninstalling built-in applications"