Single word request: a word between "projects" and "activities"

The context is time planning. Specifically, how to name these activities/projects/? that are needed for achieving your vision/dream. Which word would describe (cover) the following activities the best?

learning to play guitar
writing a scientific article
writing a new song
learning a new skill

Possible suitable words

Project - is used for more extensive activities than described above?

Activity - is often use for very small activities (e.g. going for running)?

Or are there any better words?

Solution 1:

undertaking (n.)

Something undertaken : ENTERPRISE m-w

The restoration of the old theater is a huge undertaking.

A task that is taken on; an enterprise. Lexico

undertake (v.)

To take upon oneself: set about: ATTEMPT

undertake a task
undertake to learn to swim m-w

Commit oneself to and begin (an enterprise or responsibility); take on.

A firm of builders undertook the construction work. Lexico

Autonomous activity implies a goal toward which it is directed or an undertaking of which it is a part.
...
Ms. Jones, for example, may autonomously undertake to learn to play the piano. Charles Lidz; The Erosion of Autonomy in Long-Term Care

One of the best early tasks you can undertake to improve your journal article is to write an abstract—something that describes your article's topic and argument. Wendy Belcher; Writing Your Journal Article in Twelve Weeks

A travel piece about all of New York City might seem like a big undertaking because it is. Kerrie Flanagan; Writer's Digest Guide to Magazine Article Writing

"I know what you can do," she said. "You can write your own songs. Everyone does it...They'll jump at the idea of their lead singer writing her own stuff..."
...
"I don't know," she said doubtfully. "It's a big undertaking, a big risk..." Nicholas O'Hare; Fly!

Most kids need short, attainable goals to keep them interested in the big picture, and they need some immediate success to keep them positive about learning new skills.

The best chance for success with any large undertaking is to breakdown big projects into small, manageable blocks with a definite beginning and ending. For music lessons, agree with your child to commit to five lessons—and accompanying practice session—at a time. L. Berkenkamp and S. Atkins; Because I Said So!

Undertaking appears to have a broad scope, between simpler tasks and larger enterprises. It can also be used as a verb, undertake, an advantage over some of its synonyms.

Solution 2:

When you are describing things that are personal— learning to play an instrument; write a song— the English term is "aspiration." Those are things you want to do ('aspire to') for your own satisfaction. So they are not really 'projects' or 'activities'. 'Activities' are things you do, rather than things you desire. 'Projects' are often related to work, school, or even home, and they are something discrete, rather than a long term goal.