Euclid in Elements uses phrases like
A circle is a plane figure contained by one line such that (...) [emphasis added]
which vaguely resembles your idea about a boundary. However in Elements we won't find a rigid notion of a intersection - the crucial word you had used.
Lack of explicit definition of a intersection is a valid objection. We can rise it from the very beginning of Elements.
Take Theorem 1 (see picture). It states that on a given finite straight line AB it is possible to construct a equilateral triangle ABC by drawing two circles with radius AB, and center in A and B. Then letting C to be a point where circles intersect. By drawing AC and BC we constructed equilateral triangle ABC.
But there is no way to make sure that circles will intersect using previous statements! Without notion of intersection we can't even construct equilateral triangles on a given line!
Thus in modern euclidean geometry new postulates, which resembles your proposition, are added. Below are two from The Non-Euclidean Revolution by Richard J Trudeau.
Postulate 6. (i) A circle (or triangle) separates the points of the
plane not on the circle (triangle) into two regions called its outside
and inside (see Figure 21); (ii) any line drawn from a point
outside to a point inside intersects the circle (triangle); and (iii)
any straight line drawn from a point on the circle (triangle) to a
point inside will, if produced indefinitely beyond the point inside,
intersect the circle (triangle) exactly one more time.
Postulate 7. (i) A straight line extending infinitely far in both
directions separates the points of the plane not on it into two
regions called its sides (see Figure 22); and
(ii) any line drawn
from a point on one side to a point on the other side intersects the
infinite straight line.