In cross leg poses you can twist, side bend and forward bend while sitting with legs crossed. You can also "lift yourself up."
If you have difficulty sitting upright with crossed legs, then an option is to sit with one shin folded to the outside of the thigh in a semi-kneeling posture. This is also a good option if you have difficulty bending forwards with legs crossed.
While sitting cross legged you can practice backward bending and forward bending the spine. Start by lifting and lowering your tailbone so that your lumbar spine alternately bends backwards and forwards, then carry the bending actions up into the thoracic spine. This is a great way to build pelvic awareness.
While sitting with legs crossed you can twist your spine with the help of your arms. Or you can put your hands together in prayer in which case you have to use the muscles of the waist and ribcage (the obliques and intercostals) to drive the twist.
You could also stretch the shoulders.
You can stretch the shoulders while sitting cross legged by clasping the hands and reaching the arms rearwards behind the back. You could also touch them together in prayer behind your back.
You could also stretch the shoulders with the arms in front of the body using the eagle pose shoulder stretch. Another option is the cow face arm position.
To stretch the back of your hips you can bend forwards while sitting cross legged.
While bent forwards try increasing the forward tilt of you pelvis. Push your pubic bone down and back. Pull your tailbone forwards and up. So that your hip muscles are active, try pressing your feet downwards into the floor.
Try to make your arms feel long. Reach your shoulders forwards and make your palms feel open. To add a slight twist lift one arm while pressing down with the other hand (not shown.)
To add a side bend for your spine, reach your arms to the side while bending your upper body sideways. Bending to the left try to expand the right side of your waist and ribcage. You could work on reaching your right-side-ribs away from your pelvis while pulling your left-side-ribs towards your pelvis.
Another option for the cross legged seated yoga pose is to bend forwards and reach an arm across the chest to the opposite side. Then sink the shoulder and ribcage on the side of the arm you are stretching.
Reach the other hand forwards.
From the shoulder stretching position you can bend the elbow and use the shoulder to press it into the floor so that the ribcage lifts.
Then put the hands together in prayer and use both shoulders to drive the twist.
A very simple cross leg stretch is to reach your spine and arms upwards. Work at lifting your ribs up away from your pelvis. Draw you head away from your ribcage. Reach your shoulders up and at the same time make your arms and fingers all feel long.
So that you get a better feel for the action you can relax arms and spine while exhaling then continually lengthen upwards while inhaling.