Are lava flows dangerous to people who live hundreds of kilometers from an erupting volcano?
Yes, the lava wound necessarily kill you but other volcanic issues could. The ash, gasses and other tiny tephra can get caught up in the atmosphere and cause it to be polluted.
A sleeping volcano is a volcano which hasn't erupted in ages but has erupted in the past and will carry on erupting in the future. Another name for a sleeping volcano is a dormant volcano. Volcanoes can go through a dormant or sleeping phase sometimes lasting for hundreds of years before reawakening and erupting again. Volcanoes with no geological activity are "extinct", and will never erupt again.
A volcano that has erupted at least once during the past 10,000 years is called an active volcano. Active volcanos can be further classified as erupting or dormant. An erupting volcano is an active volcano that is currently having an eruption. A dormant volcano is an active volcano that is not erupting, but that is due to erupt again.