#1 Can doughnuts, and other wet batter items, be fried in this, please?
Although it's classed as a deep fat frier, it's actually because of the rotation of the basket that achieves the results. It's NOT a DEEP fat fryer. It's more like a shallow fat fries that acts as a deep fat frier. I wouldn't reccommend putting anything covered in wet batter into it unless it is very small.
#2 Does the filter prevent the kitchen smelling like the local fast-food outlet?
Have used to fry chips, battered fish and veg and also various Indian snacks and little or no smell - much better than open frying in a pan. Filter needs cleaning, but rinse under water or in a bowl with a little washing liquid.
#3 Can you cook home made battered fish in this fryer?
Would not recommend it. The fish and the batter would cook well,,,BUT... The basket rotates at an angle so quite a bit of the batter would run off before the outer skin of it had set. This would contaminate the oil.