Can I push my wheelchair with my foot?

Only if you can't propel the chair using the wheels because of lack of capacity. In that case you may push with one foot, but no part of that foot may touch the ground:

• during the forward swing of your stroke, including when the racket hits the ball; or
• from the start of your service motion until the racket hits the ball.

Breaking this rule loses you the point.

Otherwise, using any part of your feet or lower limbs against the ground or a wheel while serving, hitting, turning or stopping during a point loses you the point.