You should firstly do the flooring and then false ceiling to get straight eye view level. This is an advice from my daughter-in-law who's an interior designer.
The main reason to use PVC is, when house roof is not cemented or made of steel sheet, there will be water leakage sooner or later, so you cannot use gibson so only option is pvc.
Melamine and PVC are completely different. Melamine is a organic compound while PVC is a polymer of monomer Vinyl Chloride. Dimpu is using PVC not Melamine. Usually melamine is used to make kitchen utensils.
Heartiest Congratulations 🎊 👏 💐 🥳 Dimpu.All your efforts payed off. You have a new home & new Mahindra Thar.You are well settled 😉 👍 .Goodluck to you.May God bless you with more success 🙌 in you life.