I have three questions I'm hoping to get help with.

1) I'm wondering if someone could help me identify the inductors L1 and L3 in the circuit. I see L2 and that makes sense to me as a single inductor, but for L1 and L3 it looks like an inductor with an iron core on one side and a variable cap...Did I read that correctly? Is that typical for some applications and is there a common name for this inductor and cap setup? Bonus points if you know the purpose of the components

2) Would you agree that there is 4 way connection within the red circle?

3) Why list a schematic with polarized caps? I guess the benefit is it gives you the option to use polarized or unpolarized caps, but is there any benefit to unpolarized caps...are they usually smaller or something? Am I missing something else? Why not just always use unpolarized caps? Thanks in advance!

 

The C3-L1 and C5 -L3 are parallel tuned circuits, High impedance at resonant frequency.
https://rimstar.org/science_electronics_projectslc_circuit_aka_tank_or_resonant_circuit.htm
Max.

 

The C3-L1 and C5 -L3 are parallel tuned circuits, High impedance at resonant frequency.
https://rimstar.org/science_electronics_projectslc_circuit_aka_tank_or_resonant_circuit.htm
Max.

Pretty cool, thanks so much! Tried the link you posted but looks like it doesn't lead anywhere. I searched and think you meant this link:
https://rimstar.org/science_electronics_projects/lc_circuit_aka_tank_or_resonant_circuit.htm