The 5th lord is Mars but the child studies in the West. Is that wrong?
See in which direction the 5th lord sits. If it sits in the West, that is excellent; if in the East, choose the East. The East and North are best for study anyway, and if the lord sits in the South, studying in the South also works.
Related questions
If a house has four members, whose kundli should be used for its vastu?
Primarily the grih swami's, the person whose money is going into the house, because the house affects the owner and his next three generations; do not go by the name the property is registered in, such as a daughter. The facing and main door are chosen from the grih swami's chart, for example North if his Mercury is exalted or his North-side planets are strong. Where a child sleeps or studies is decided from the child's own chart: if the child's Mercury is weak, seat him in the South instead of the North, following the 180-degree rule for a weak planet.
Can a mirror be fitted on a wardrobe in the S, SSW, SW, WSW or West?
No. Wardrobe mirrors also belong on the North or East wall. Some say the North-West is also allowed because the mirror represents the water element and the Moon.
During Diwali puja the deity faces South and we face North. Is that right?
No, it is wrong. Seat the deity in the West facing East, and sit so that you look at the deity while your face is towards the North. The Lord's direction is what matters, just as the teacher's direction matters in a classroom.
How far does the influence of a devta reach beyond its own pad?
As in a kundli, where Jupiter blesses whatever it aspects with full drishti, a devta also aspects the devta opposite it; Surya, for example, balances Varun. If you cannot balance a devta directly, balance the devta whose full drishti falls on it, and its gaze will set it right.
If the Sun is debilitated, can a Sun picture be kept in the East?
No, do not keep it and do not take on the trouble. Strengthen the West instead; its power reaches the East on its own.
If the chart has Gajkesari yoga, which direction should be in good order?
The ishaan (North-East) should be correct, along with the North and the East.