Even though I am not required to file a federal & state return, only income is SSI, I would like to anyway for the record. Will Turbo Tax allow me to for free?

Be aware that if you have NO income other than SSI or SSDI, you will not be able to e-file, but you can print, sign and mail the return.  Keep a copy of it for your own records.

Yes, you can.

Please read the attached article for reasons why filing with no income may still be a good idea: https://turbotax.intuit.com/tax-tips/irs-tax-return/can-i-file-an-income-tax-return-if-i-dont-have-a...