Oh, this could be a looooooong answer.
First of all: yes, the kiss on Jay Leno is real. They do kiss, but I guess it was somewhat planned because they did this as a sort of stint to promote his movie. (And ever since I am silently praying that either one of them appears on another talkshow as a surprise guest, because how fucking cute would that be?! Their support for each other is the most adorable thing ever!)
The other kiss was also real, yep. Though that one looked more of a spontanious action to me. It’s the one when they were filming in London and they were on the Johnny Show (I think), it’s a time during which they seemed incredibly close to me anyway. There’s also that photo of them where they kiss outside of the studio from that time.
One of them hand holding… do you mean the one from behind the scenes from Cougar Town? I assume not because you’re refering to the fact that it was all before Mondler happened…
Just guess they were and have always been super close. They probably fucked each other at one point too, but realised it didn’t work out (for whichever reasons, or this might just be my imagination going wild again).
And please don’t get me started on their “friendship” - it’s very extraordinary and I’d rather classify it as an “almost lovers/secretly married” relationship than an ordinary friendship. After all, she loves him 13.6 on a love scale that only reaches from 1 - 10. Nuff said.