Almost missed this question! A quick rundown for the Connections:
-Tamagotchi Connection models V1, V2, V3, V4, and V4.5 can all connect together. It can either be two of the same version (a V1 and a V1, for instance, and in the V4's case it shares the same base programme with the V4.5) or any of each! So a V2 and V3 could connect the same way a V1 and a V2 could connect, and in your case - yes, a V1 and a V4 can connect and, after enough play sessions, can marry each other.
This page on the Tamagotchi wiki goes into more detail about it!
-However, Tamagotchi Connection models V5, V5.5 and V6 are not compatible with the prior versions listed. These models can, however, link up and visit each other instead, although the V5 and V5.5, if I remember correctly, cannot marry a V6 and vice-versa. Watch out! Only the two of the same version method works for these models in the case of marriage, due to how differently they play.
Hope that helps!