Your Tamagotchi is eligible for matchmaker visits when it is at lesat 72 hours into the adult stage.
The times that the Matchmaker will come are:
10.30am
3pm
7pm
So if you want to summon the matchmaker, just set the time to 10.29am, 2.59pm or 6.59pm and wait one minute- if your Tamagotchi is eligible for matchmaker visits the matchmaker will come.
If you don't "summon" the matchmaker, good luck to you in catching the Matchmaker. (She only appears for a whopping 10 seconds on screen!)
Any version below the v5 can mate with any other version below the v5. What I mean is, the v5 can ONLY mate with a v5, but...
v1 can mate with v1, v2, v3, v4 and v4.5
v2 can mate with v1, v2, v3, v4 and v4.5
v3 can mate with v1, v2, v3, v4 and v4.5
v4 can mate with v1, v2, v3, v4 and v4.5
v4.5 can mate with v1, v2, v3, v4 and v4.5