Exemption under section 80G cannot be availed if we opt for new tax regime
To the best of my understanding there is no alternative provision under the IT Act to claim such benefits
Yes
One will have to work out the tax liability under both the schemes and decide the on the regime. There is no “one size fits all” formula for this. Old regime may be beneficial if an individual has an ongoing home loan. Plus the other deductions that are avaliable