There can be for poorly installed flex duct.

However properly installed,using even a short length of flex on each branch significantly reduces sound transmission.

In the states I can buy a small inverted wire basket thing that fits into the hole where the downspout attaches to the trough.

It keeps.leavea from clogging the downspout and helps keep.water flowing even when hotter is getting full of leaves

If you can't find a zinc elbow you may be able to use a rubber fernco type setup

Citronella oil will burn nicely

Explode, no.

Yeah but no one can see it back there.

Look for a door knob reinforcement plate.

Measure both the thickness of the door and the backset of the latch to make sure you get the correct one.

Not those products,they are waterproofing/crack isolation membranes not primers.

They do sell and recommend a latex primer.to use under SLU.

The paint should be ground off or hit and missed at minimum

I'd say it's the foundation of the chimney.

Likely the original mechanicals vented up through it, and if you strip the drywall you'll be left with a large chimney.