For Yandex maps: WGS-84.
For the rest: WGS-84 Web Mercator.

I don't know how you got your coordinates.
So I can not be sure that they are not correct.

Here is my version of the script and a screenshot of the result.

using UnityEngine;

public class Circle : MonoBehaviour
{
    public float lng, lat;
    public float radius;
    public int segments = 32;

    private void Start()
    {
        Vector2[] points = new Vector2[segments];
        float s = 360f / segments * Mathf.Deg2Rad;

        for (int i = 0; i < segments; i++)
        {
            float x = Mathf.Cos(s * i) * radius + lng;
            float y = Mathf.Sin(s * i) * radius + lat;

            points[i] = new Vector2(x, y);
            OnlineMaps.instance.AddMarker(points[i]);
        }

        OnlineMaps.instance.AddDrawingElement(new OnlineMapsDrawingPoly(points, Color.red));
    }
}

List<Vector2> polyList = new List<Vector2>()
        {
            new Vector2(82.66599f, 81.30697f),
            new Vector2(74.36659f, 82.58331f),
            new Vector2(60.97482f, 82.9713f),
            new Vector2(48.66783f, 82.27274f),
            new Vector2(42.27214f, 80.82545f),

            new Vector2(41.33019f, 79.10966f),
            new Vector2(43.90862f, 77.46705f),
            new Vector2(48.56174f, 76.1094f),
            new Vector2(54.38786f, 75.16797f),
            new Vector2(60.79885f, 74.72003f),

            new Vector2(67.35206f, 74.79962f),
            new Vector2(73.63844f, 75.40077f),
            new Vector2(79.18523f, 76.47713f),
            new Vector2(83.33164f, 77.93685f),
            new Vector2(85.03754f, 79.62836f)
        };

        OnlineMapsDrawingPoly poly = new OnlineMapsDrawingPoly(polyList, Color.red);
        OnlineMaps.instance.AddDrawingElement(poly);