1. The best answer is "No, there isn't one available". In English, you could repeat the word 'baby-cot' in the answer but we like to use 'one' or 'ones' a lot. Your answer misses the key fact that the negative in English needs to use 'do' or 'does' before the main verb, for example - 'It does not have a cot'. But if the question uses 'is there…?' then use that form in the answer.
2. The question form is a bit strange…we prefer to say 'Are there two bedrooms' rather than make a statement and add a question tone. The best answer is 'No, there is only one bedroom' - you must use the singular 'is' and we would also add 'only'.
3. You need to add, like in Q1, the 'do' auxiliary, so the best answer is 'No, I don't have a washing-machine' (we also use 'I haven't got a washing-machine'. You can't say 'I not have" ...it must be 'I do not have/I don't have'. Also in English 'laundry' means either a place like a factory or shop where people wash clothes or it means your 'washing', that is the clothes and sheets you need to put into the washing-machine. It does not mean a machine for washing clothes.