My Verna too had that issue with the boot release the rubber gets hard and flakes off, did not changed it used as is.
On the i20 too have the same issue quoted 2k to replace the switch, but then they said it’s working use it Till it stops working.
someone up in the thread asked about injector cleaning. Well petrol injectors too get dirty and affect spray pattern.
I was having misfire conditions on heavy acceleration, changed plugs and coil did not help.
opted for them to remove and clean the injectors they were dirty, but the problem stayed intermittent, I then put a bottle of gumout ram it more concentrated than directed, issue resolved.
service guy said to use premium fuels once in a while if not often.
with regards to cabin filter, previous Verna the one I had was 2011 it had the washable mesh filter. It would not filter much and the evaporator core would get clogged up. Had done the evaporator removal and cleaning once in between it was really plugged up and filthy. Before the accident the same low airflow symptoms I noticed.
the i20 has the pleated paper filter, have spent around 3300 so far on filter changes. Still cheaper than removing the evaporator and dash and manually cleaning. What’s more better is not once got that foul odor from the AC. On the previous Verna with washable filter that was often.