Ann: June Quarter Activities Report and Appendix 5B, page-6

"Can someone help me with a query on tax return for 24-25? If you are retiree trying to make a living out of share trades, then the 1st of $18,200 is tax free right?"
Yes. As @Bazz58 said, everyone (i.e. retirees and non-retirees) have access to the $18,200 tax-free threshold associated with personal income.

"But all goggle search is advising that all CGT will be taxed even if you are a retiree."
In very general terms, being a retiree doesn't exempt you from from paying income tax, including CGT. What matters is whether your taxable income, including assessible capital gains, exceeds the tax-free threshold of $18,200 p.a.

The way to think about CGT is to perform the relevant calculations to work out the assessible taxable capital gains. This number is then added to whatever other income (from various sources) you might have to arrive at your (total) taxable income, which the progressive (sliding) tax scale then applies to.

"Understand if you are earning above $18,200, then $0.16 apply for evry $. Is this the correct assumption?"
Yes, but only for the current tax year (FY2024-25). If your question related to tax return prep for the the recently completed tax year (FY2023-24), then it will be 19c for every $1 of taxable income earned between $18,201 - $45,000.