As per your second question it appears that your 1st query is resolved.
For your Second Query, Yes you will have to pay taxes on the entire 80K and not on the balance 50K. Since spending money to your parents is your personal responsibility and has no bearing or relation to the income that you are earning from the rent. So it is a mere application of funds and not an expense in Income Tax per se.
And in the case of Income Tax you get a Standard Deduction of flat 30% u/s 24B on the amount of rent that you earn. So technically speaking if you earn rental income of Rs.100/- you get a deduction of Rs.30/- and you pay tax on the balance Rs.70/- only.
Trust this clarifies your query.
Feel free to call / get back in case of further clarifications.
Rohit R Sharma
BCOM, ACA, LLB-GEN, CERT. FAFP