query #3:

select a.fname, a.lname
from actor a, casts c, movie m
where a.id = c.pid AND
c.mid = m.id AND
(m.year < 1900 OR m.year > 2000)

query #5

select a.fname, a.lname, m.name, COUNT(DISTINCT c.role) AS roles
from actor a, movie m, casts c
where a.id = c.pid AND
c.mid = m.id
group by a.fname, a.lname, m.name
having roles >= 5;