Is there any way to show unique ads on all blocks?
No you can't, as far as I know. The only time this was avoidable, was when the Ad Balance tool was available. Now, it can also be the expression of a lack of inventory at that time.
Unrelated, today, while checking the Ad review center, on the first page, I have a video ad, auto playing, with sound. this is an adwords advertiser, but I thought advertisers didn't have the right to have auto play video, and worse with sound. Isn't it ? I also thought it was among the things which would cause Chrome to block ALL ads on a site, in a future version (next year).