1. When there's demand
2.Yes, their value in USD. Alts tend to go up against BTC when its price is stable.
3. Maybe never?
Alts tend to go down in BTC. Their price is correlated to BTC and USD.
99% of alts always go down in BTC longterm because they die. Only a few alts price is correlated to USD or CNY, those that will survive even if BTC dies(XRP,NXT,BTS).