Unboxing my VT50 65" USA version

Not so sure about used...but sounds like it was opened.

My GT50's foam blocks weren't taped, and there were no Viera stickers on the bezel - yet it was brand new. Not all examples have stickers on the bezel.

Was the packaging for your remote and owners manual booklet still sealed? Was there any protective static cling film on the TV's bezel that you had to peel off?

When you first plugged it in did you get the menu that tells you to choose HOME or STORE mode?

Go into the Service Menu and check the hours used and times it's been turned on.

I've never seen a Panasonic plasma with taped foam blocks, so nothing to worry about there. As far the corner sticker goes, they are not included with every TV. Generally those are more common during early production run models, since that's around the time that retailers will be unboxing new models for store display. For example, my VT50 came with the sticker (purchased in May 2012) but my friend's GT50 did not (purchased in Nov 2012). Sounds like your TV was new to me.