Plug all the flex cables back in. Turn the phone on. Let the phone boot up with the long apple logo issue.
Once it's booted. Go to voice memos app and see if you can start a voice record. If it can't start the audio IC has gone bad.
Also you can try making a call. If speaker phone is greyed out then that is another symptom the audio IC has gone bad.
Also the long apple boot 5 minutes is also caused by audio IC fault (can also be baseband at fault but that would search in no service / searching issue).
A bad front cam / home button flex can cause long boot too, note that if the phone is working fine for example you can boot the phone normally without long wait with home button plugged in but front camera unplugged.