I am in the UK.

I have been cleaning out the dust from the inside of my monitor and I
just moved a few pots to make sure their tracks are clean and returned
the pots to how they were.

In fact the only pots I can find are three right next to the coil on the
neck of the picture tube and they are marked:

Y-HC: Y and in small letters, HC
Delta V: capital delta symbol then V
YV: Y and in a small letter, V

What do these do?

To be prfectly honest I think I may have not quite returned them to
their original postion but might be 20 or 30 degrees out.

Can I adjust them with the monitor on? Of course I won't be touching
any HT parts but I wonder if they are inherently too close to the HT to
adjust while the monitor is on?

Must I use an insulated trimming tool rather than a meta scredriver?