iphone 13 extremely hot after ios 26.1 upgrade and battery drains very quickly with no ios 18.x signed version any longer for downgrade...help!

iphone 13 extremely hot affter ios 26.1 upgrade and battery drains very quickly. I have disabled all the new facy settings and updated all the application to the latest and restarted also reset settings to factory defaults which was a slep because I had to resetup a lot of my apps but nothing works. It keeps getting very hot and now no signed version of ios 18.6.2 still available to downgrade to....where to now please?