Can drinking 2-3 cups of hot decaf flavor tea everyday b harmful, is it true it slows down metabolism?digestion?can it help in weight loss?

No harm: Unless it is scalding hot and burns tissues, unless you have calcium oxalate kidney stones (tea is a rich source of oxalate), it is not harmful, and might have some health benefits. Hot beverages can stimulate bowel function (although tea can be constipating-tannin content), supply antioxidants. Unlikely to be clinically significant in weight loss (unless you eat less).

Depends: Flavored tea can contain sugar or artificial colors & sweeteners that can be harmful. Green tea (brewed, not instant) contains powerful antioxidants including epigallocatechin gallate (egcg) which increases fat burning. Antioxidants also support the immune system. Ginger tea, an herbal tea, aids digestion. Many of the herbal teas have other beneficial effects such as being calming & soothing.