You have all the powers that Putin currently does. Everyone completely loyal to Putin is now loyal to you. Enemies of Putin are enemies of you. Putin no longer exists, and there has been a clean and absolute transfer of power to you. The economic, military, social and political situations are the same as they now are. You are not inhabiting Putin's body, you are just you. You're magically transferred to the Kremlin. The world at large doesn't know your past life, to them you have magically appeared as the new ruler. To everyone who knew you before, you just vanished.
Edit: no one knows your past life YET. They'll quickly figure it out. You will not lose any support based on your actions in your past life.
Immediately start figuring out how I can disappear. I am not cut out for the world Putin lives in.
But assuming I'm staying in the job, I find oligarchs who have been personally impacted particularly badly by western sanctions and share with them that the war has become too costly. I know I can't openly just change my mind, because too much of the apparatus below me would gut me for it and nobody on the other side would believe me. So we're orchestrating a coup against me. If you just let me fuck off, I will, and we'll set it up so that you're taking the reins off of me. Powerful figures that have legitimate grievances against the ongoing costs of the war are going to forcefully oust me and offer peace. I'll try to pick one who will actually do that. Someone who stands to profit enormously from better relations with Europe.