Hardware failure on Iphone 11 pro max, happening on Software updates

I updated my iphone by June and after update i started getting couple of issues.

Issue 1:

While charging i saw the phone is getting extreme heat and sometimes it show message - Charging is disabled due to excess heat and will be resumed after sometime(i am using same charger and wire i got from box)

Issue 2:

All of sudden battery health went down to 78%

Issue 3:

All of sudden i saw phone getting heated up sometimes when i was in call for more than 10 mins

Issue 4:

I have some dust in phone speaker and while i was checking with authorised service provider in India, they charged me 600Rs(July 2023) and they ran some diagnostics test and said my stereo speaker have some problem and on running test again they said they unable to identify the issue.

Issue 5:

I was in a call for say 15 mins, suddenly my phone got restarted after ending the call. And after that it was keep on restarting repeatedly

Resolution tried:

1) I went to authorised apple service provider and he said he can restore the OS but data will be lost. I gave him for restore but he returned saying he cant able to install the software(Aug 10)

Issue 6:

Once after service person returned the phone start showing message - support.apple.com/iphone/restore was getting displayed

2) I went to 3 more authorised apple service provider in india, but they too mentioned that we cannot fix the issue and go to Apple owned store

3) I went to one of apple owned store in India and explained the issue, they restored with latest software version on Nov 6,2023. The phone got restore completed successfully but after a while it got restart again.

4) Store service person said that it is hardware issue and that whole unit should be replaced and they will not be able to repair it.

Now i m facing frequent restart from my mobile and unable to use it