1. Yog is a religious concept and non-Vedic i.e. other than Hindus can not adapt yog as a lifestyle.
This is a myth that non-Hindus can't adapt yog as a lifestyle but yes this is absolutely true that yog is a religious concept. Yog is the final destination for all the religions. All the religions finally merge into yog just like different rivers come from different ways and finally merge into the ocean, same is with yog and religion. Let it be any religion, it finally merges into yog. In Christianity we call it Self-realization, in Islam we call it Vasla or Deedar, in vedic religion or Hinduism we call it Atmasakshatkara. All is yog. For being religious one has to become yogi and to adapt yog as a lifestyle.

2. One can loose 3 to 4 kgs of weight in 2 to 3 days through yog practice.
Yog is a science not a magic, its true one can loose weight through continuous yog practice but 3 to 4 kgs in 2 to 3 days is not recommendable as it may become threat to good health.

3. Cancer and Aids patients can be medicated through yog.
Yog practice can of course increase the immunity level of an individual and make him fit but absolute medication of such crucial disease is not possible.

4. Yog therapy is a substitute for medication
Yog therapy is not a substitute for medication; but it is a vital adjunct to the surgical procedures, psychotherapy and medication. A continuous practitioner needs not to take any medicine as his immunity level increases.

5. Yogis are unmarried.
God himself is a Grehasti to look after his entire Universe, his big family. If we go back in history all the yogis were Grehestis i.e. married. Let it be Yogiraj and Natraj Shiv, Yogeshvara Krishna, Marayada Purushottam Ram, Yogi Raja Janak or Guru Ram Krishna Paramhansa, all were married and the real yogis who made a balance in all of the aspects of their life, and this is what Yog is all about… balance and harmony.

6. Yog means meditation / Yog means pranayam or breathing exercises/ yog means physical exercises.
Yog is not only meditation, not only pranayam and not only a set of physical exercises. Pranayam, asan i.e. physical exercise and meditation all are parts of yog and hence yog is complete lifestyle in itself. Yam, niyam, asan, pranayam, pratyahar, dharana, meditation and Samadhi all are different parts of yog and when one joins these different parts then only it is called yog.
'Yog and Meditation' is a wrong phrase as meditation is already there in yog.

7. Yog practitioner or Guru should be serious, and should never laugh.
Laughter is the divine gift of God to human beings… Only Yogi, the yog practitioner can laugh and enjoy every moment of his life.

After each session Attahas i.e. laughter is practiced, as it's the best exercise for body, mind and soul.

8. There is no sweating in yogic exercises hence aerobic or other form of exercise is the substitute for this.
There are fast exercises in the Bharat Yog, the traditional and original form of yog, which are known as Drut Kriyas that are there for calorie consumption and helps in sweating.

9. One should be flexible for practicing yog.
Shri Krishna said to Arjun 'tu jis bhi sthiti mein hai meri or chal mein tujhe prapt ho jaunga' You have to begin your journey right from the station where you are standing, don't wait for getting rid of the vices, just start walking on the path of yog and vices'll be removed naturally.