Hi there,since Batumi is an Autonomous Republic,if i wanted to make a side trip to Batumi from Tbilisi,do i still need a visas to make it through?thanks.have a good day everyone!!
No, there are no "border" checks between Batumi and Tbilisi. You do not require an special paperwork.

Like with almost all of the so called 'autonomous republics in former Soviet countries, also here there are no border checks (if there is - other than on paper - a border at all) so visa required.
Matthijs
Once upon a time, there used to be a real "border" between Adjara and the rest of Georgia, but that was way back in 2004, before Aslan Abashidze was deposed.
Since 2004, Adjara has been "autonomous" in name only. It has a few special rights under the Georgian constitution, but is otherwise an ordinary province of Georgia. There are no border controls between it and the other Georgian provinces, and it's unlikely you'll even notice the border when you cross it.