I am 23 and I tried to gain weight but it is hopeless, would babies cerelac work?

Not hopeless. You could have a problem absorbing food. Avoiding lactose and gluten might help. Also avoid alcohol, tobacco products, and processed food. Read kelly mcgonigal's the will power instinct to learn to mange stress skillfully and make healthy life style changes. Healthy fresh vegetables, fruit, high quality protein, good fats, and starches, a good night sleep, and exercise aerobic and resistive helps.