If you answered 'Three', then you are wrong. You can hope for three, but what does partner do with these type of hands?

Take (i). Partner has no choice but to put you back to 2 ♥. Passing 2 ♦ and leaving you in a likely 4-2 fit is clearly inferior. And any other bid (eg 2 NT, 3 ♣) is pie in the sky, with six measly points.

With Hand (ii), partner could sensibly pass 2 ♦. But there are good reasons for partner to put you back to 2 ♥. (a) a 5-2 fit plays better than a 4-3 fit. (b) partner's bid of 2 ♥ gives you another turn if you have a really good hand (your 2 ♦ rebid did not really limit your hand, as you'd almost never bid 3 ♦).

The bottom line is: if partner puts you back to your first suit, you should (until further notice) treat it as a begrudging preference, rather than actual support.

So after you have opened 1 ♥ and the bidding has proceeded l♥-1 ♠-2 ♦-2 ♥, you should only go on to 3 ♥/4 ♥ with six hearts. Holding a good hand (and you'd need a good hand to proceed, as partner has shown only 6-9 pts), but without the sixth heart, you should find another forward-going bid.