Mistakenly selected old tax regime. Can I change it to new tax regime anyhow

Can I change the regime for 23-24 while filing the return? Or is it not possible anymore?

Need advices from folks who have done or know about the tax regime.

I have selected Old Tax Regime in my tax planning initially at workplace but during filing ITR i am thinking to switch to New Tax Regime.

Is that possible?

1. Currently in new tax regime. Want to shift to old regime for 24-25. When will I get to choose?
2. Can I reside and work in Bangalore and claim HRA on a house in my home town?

Inspite of so many "better than earlier govts" reforms in the last 10 years...the govt hasnt done much needed reforms in the income tax regime.

The govt is doing a few good things like dissolving inept psu's, selling off entities like A...