Please help me

Dear Student,
Answer to Q1.2) Combination reactions are those type of reactions, where more than one substances combine together to form a single substance. There are three type of combination reactions:-

a)Combination in between two elements.
for example: Combination between magnesium(s) element and  oxygen (g) element gives magnesium oxide, which is a single compound.
b) Combination in between a compound and an element 
for example: Combination between oxygen(g) element and carbon monoxide(g) compound to give carbon dioxide,  which is a single compound.
c)Combination in between two compounds 
for example: Combination between ammonia(g) compound and  hydrogen chloride (g) compound gives ammonium  chloride, which is a single compound.

Answer to Q1.3) The product formed is magnesium oxide. It is the combination reaction of pure magnesium(s) getting burnt in air
(O₂), to form magnesium oxide(MgO)

Answer to Q1.5) The combination reaction between quicklime and water is
CaO(s) + H₂O (l) $------>$Ca(OH)₂ (s), Calcium hydroxide (Slaked lime) is formed.
Please ask the remaining queries in the next thread.
Regards