Can leg training only practice squats, hard pulls and heel lifts?

Yes, you can only do one thing. But in this case, the practice is not perfect.

Barbell (squat, squat, squat), straight leg hard pull, heel lift in standing position and heel lift in sitting position.

Stretch your legs in a sitting position ... I'll tell you another good way to "kick the ball" so that your leg strength can be well exercised.