This is a good answer to exercise 1b: 

select r1.role as role, p.name as name, m1.title as movie_title, m2.title as tv_movie_title
from plays_role as r1
join plays_role as r2 on r2.person_id = r1.person_id
join movies as m1     on m1.movie_id = r1.movie_id
join movies as m2     on m2.movie_id = r2.movie_id
join people as p      on p.person_id = r1.person_id
where r1.role = r2.role
  and m1.type = 'movie'
  and m2.type = 'tvMovie'
order by r1.role, p.name, m1.title, m2.title;

This could also be written as

select r1.role as role, p.name as name, m1.title as movie_title, m2.title as tv_movie_title
from plays_role r1
join plays_role r2 on r1.person_id = r2.person_id and r1.role = r2.role
join movies m1     on r1.movie_id = m1.movie_id   and m1.type = 'movie'
join movies m2     on r2.movie_id = m2.movie_id   and m2.type = 'tvMovie'
join people p      on p.person_id = r1.person_id
order by r1.role, p.name, m1.title, m2.title;

However, some people prefer the style where the on-clauses contain only the join predicates. 

Below are some solutions that could be improved.

1) We could "simply" the final where-clause using nested joins:

select r1.role as role, p.name as name, m1.title as movie_title, m2.title as tv_movie_title
from plays_role as r1
join plays_role as r2 on r2.person_id = r1.person_id
join (select * from movies where type = 'movie')   as m1 on m1.movie_id = r1.movie_id
join (select * from movies where type = 'tvMovie') as m2 on m2.movie_id = r2.movie_id
join people as p on p.person_id = r1.person_id
where r1.role = r2.role
order by r1.role, p.name, m1.title, m2.title;

This is not ideal in that it is hard to read and may confuse a query optimizer.
(HyperSQL does not optimize queries so it is actually less efficient.)

2) This query takes this idea one step further by folding into the nested query the join with people. 

select m2.role as role, m2.name as name, m1.title as movie_title, m2.title as tv_movie_title
from (select person_id, name, role, title
	     from movies
	     join plays_role on movies.movie_id = plays_role.movie_id
	     join people on plays_role.person_id = people.person_id
	     where movies.type = 'movie') as m1
      join (select person_id, name, role, title from
	    movies
	    join plays_role on movies.movie_id = plays_role.movie_id
	    join people on plays_role.person_id = people.person_id
	    where movies.type = 'tvMovie') as m2 on m1.person_id = m2.person_id
	  where m1.role = m2.role 
order by m2.role, m2.name, m1.title, m2.title;

Again, when writing SQL always eliminate nested queries if you can. 

3) Here is a solution that uses the "implicit join" syntax:

select r1.role as role, p.name as name, m1.title as movie_title, m2.title as tv_movie_title
	from plays_role as r1, plays_role as r2, people as p, movies as m1, movies as m2
	where m1.movie_id = r1.movie_id
	and m2.movie_id = r2.movie_id
	and r1.person_id = p.person_id
	and r2.person_id = p.person_id
	and r1.role = r2.role
	and m1.type = 'movie'
	and m2.type = 'tvMovie'
order by r1.role, p.name, m1.title, m2.title;

This will not pass code review in most companies today.  Implicit joins, especially when many tables
are involved, are very hard to debug. Using implicit joins is now considered a "deprecated style",
although many textbooks still teach it. 

Here is another variant of the implicit join, but even more complicated: 

select	r1.role as role, p.name as name, m1.title as movie_title, m2.title as tv_movie_title
from 	plays_role as r1,
	(select * from plays_role) as r2,
	(select movie_id, title, year from movies where type = 'movie') as m1,
	(select movie_id, title, year from movies where type = 'tvMovie') as m2,
	people as p
where	r1.role = r2.role
	and not (r1.movie_id = r2.movie_id)
	and r1.person_id = r2.person_id
	and m1.movie_id = r1.movie_id
	and m2.movie_id = r2.movie_id
	and r1.person_id = p.person_id
order by r1.role, p.name, m1.title, m2.title;

Again, this style is rather hard to read and so does not scale well.