That's false, they're not at all working on replacing gas. In fact, they're quadrupling down on gas (because it's basically a necessity for baseload capacity). [1] [2]
Good question, all the emitted CO² stays for centuries in the atmosphere. What is happening if in the end they can't replace all those "dirty" backups ?
This whole plan will basically work only if this big "if" is solved and deployed.
They're currently working on replacing that with battery
(this is explained in the article)