Well seriously speaking.I don't really know the meaning of their tagline " Why so serious", I guess they mean that we have go one life so don't be so serious.
About 2nd question, When Jazz passes on roads, Other cars blows up and become bubbles because of Jazz's superiors style and design.
For 3rd one, Thats not a plant, its actually a cactus, me too didn't understood it properly but what i feel is that the guy brings cactus just to tease her wife (or whatever) and she was smart enough that she picks up the flower which was in between
I didn't exactly understood the ad but still i liked it.
I know there are many ppl here opposing jazz but no offence meant to anyone.