Yes.  The American Rescue Plan provides for new, temporary COBRA premium subsidies for people who lost their jobs or had their hours cut so they no longer qualify for group health benefits.  The law provides for a 100% premium subsidy for COBRA for up to 6 months.

No. The subsidy is limited to people whose employment was terminated (or work hours reduced) by the employer.  People who voluntarily left employment are not eligible.

No.  The subsidy is limited to people whose COBRA qualifying event involves termination of employment.  People eligible for COBRA due to other qualifying events (such as divorce or loss of dependent status at age 26) are not eligible for the premium subsidy.

You can continue on COBRA unsubsidized until your 18 months of COBRA eligibility ends. In addition, you will have the option to enroll in marketplace coverage when the subsidy ends in September.  Loss of the COBRA subsidy will make you eligible for a special enrollment period (SEP) to sign up for marketplace coverage.