Questions

Sum of numbers in the outer circle in before Arc should come in inner circle patterns in the clock wise direction next Arc.

i.e, 9+6 = 15 comes in next arc of inner circle

7+3 = 10 comes in next arc of inner circle

In the same way, 4+2 = 6 comes in place of '?'.

When atoms react they do so in order to reach the lowest energy, which is the most stable. The electrons orbitals will overlap in the way that reduces the energy the most. Orbitals of similar energy will produce the greatest stabilisation.The answer you gave isn't the whole story, it depends what species is reacting with what. The effective nuclear charge on the atom will affect the energy of the valance electrons.

Hence, the reactivity of an atom arises from the existence of unpaired electrons in the valence shell.

Indian Cricket team off-spin specialist Ravichandran Ashwin has become the fastest cricketer to take 250 wickets in the Test matches. Ashwin surpassed Australian fast bowler Dennis Keith Lillee to reach the milestone of 250 Test wicket. Thus Ravichandran Ashwin has become the sixth Indian bowler to reach 250 test wickets.