my answers:

1. Labour power is the only commodity whose use creates more value.
2. When they can’t use it to create their own commodities to sell on the market (i.e. if they have no means of production) but they can’t produce a satisfactory amount of means of subsistence on their own.
3. That workers have to resort to selling their labour power rather than using it themselves.
4. When the owner of the means of production also owns the means of subsistence necessary to buy labour power, and when labour power is continuously sold on the market by workers who has nothing else to sell. ^{(In hindsight, the “two conditions” part was probably more confusing than helpful for this question)}
5. In the worker’s maintenance – including training/education as well as preparation for eventual replacement as a seller of labour power (childcare) – which requires some quantity of the means of subsistence.
6. By the value of the means of subsistence needed to buy the labour power. The minimum value is that of the physically indispensable means of subsistence (food, water, etc.), but the actual value depends on historical conditions, including societal expectations.
7. The production of commodities and surplus value.