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Most of the circuit I understand but there's a few things which I don't get.

First, at the bottom corners of the page, theres an open circle connected to ground. What does that mean?

Second, near the third op amp from the left, there's a wire that points back at itself. Does this mean it is in a loop? What does that achieve?

Third, near the top left corner, there seems to be a little bump where V(a) intersects with the wire. Does this mean anything?

Also, the switch near the bottom right corner, is it necessary for this circuit to work (as an ecg amplifier)? enter image description here

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theres an open circle connected to ground. What does that mean?

It's a terminal so that the load can be connected to both the \$v_o\$ signal and to the circuit's ground.

near the third op amp from the left, there's a wire that points back at itself. Does this mean it is in a loop? What does that achieve?

It means both the wiper and the lower terminal of the potentiometer are connected to ground. That means that the lower portion of the potentiometer is shorted out, so it doesn't affect the circuit. This is done so there won't be a floating terminal on the potentiometer.

near the top left corner, there seems to be a little bump where V(a) intersects with the wire. Does this mean anything?

This is a "jump". It means the two crossing wires don't connect to each other. Some drawings assume all crossing wires connect unless there's a jump. Others assume crossing wires only connect if there's a dot at the crossing point.

Also, the switch near the bottom right corner, is it necessary for this circuit to work

No, the purpose of the switch is to stop the circuit producing any output (when the switch is closed).

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