I can do the butter thing, but I was taught it at school.
I can tell the difference in weight to a tiny amount.
This was proved with a 'lively discussion' when I referred to one of my kindles as 'the heavier one', the discussion ended up with me in the kitchen with my carer, my eyes closed and the digital scales in action.
In case anyone is interested, the 'heavy' one is 4g heavier.
I also do freezer tetris and still manage to have a drawer for meat, one for veg and one for ready meals / snacks.
I can also do the oven timer thing, my carer was most impressed when I started to get up and the timer went off just as I reached standing.
I'm right handed but I can do somethings left handed, including crochet, I taught myself to do it left handed so I could teach my left handed cousin. Other right handers had tried but apparently it's rare for left handers to crochet.