App version & installed?

[Grizzly]

Hi

I have upgraded from ubuntu 16.04.5 to 18.04.1, everything seems to work

I had a few apps installed before the upgrade and wanted to check if there were 
newer version(s) so top start I tried 

apt-cache policy app-name

I got

installed none
candidate a_version_#&sub-version#

I know I have the app installed (via apt install) as I can run it

I tried app-name --version (also -version & -v) 
and get -v is not valid

just

app-name 
returns the main version but not any sub-version numbers

searching under "Activities" offers to install but does not show the installed 
app(s)

this is on more than a few working apps

"IF" I (re)run 
apt install app-name

will I just have two competing version of the same app(s)