1) *Cracks knuckles*
Ok link summonning is a bit more complex then what is described for now. A link summon is the summon of a link monster from the extra deck. The unique aspect of link monsters are the link markers. Each link monster has a specific amount of link markers with a position. Effects of link monsters use these marker in some way. Decode talker gains 500 attack for each monster in a zone pointed by one of the link markers .
There are 3 requirements that have to be fulfilled for the summon of a link monster:
You need to match the requirements on the card: decode talker for instance requires 2 or more effect monsters
You need to match the amount of link markers in materials: decode talker has 3 link markers thus you need 3 monster for the link monster
You need to have space for the summon
A bit more detail and a bit spoilerish:
Now a bit info about link monsters themselves. Link monsters don't posses level or ranks. So every effect that specifies a moster having level or rank does not apply to link monsters. That's why cracking dragon could be destroyed by decode talker since the ffect specifies that he is not destroyed by a monster with a lower level. Link monsters also don't have defense points. Therefor link monster cannot go in defense mode, face up or face down it doesn't matter. That's why pulse bomb doesn't apply to decode talker. on top of all effects involving defense do not apply with link monsters. Shield and sword does not apply to link monsters.
2) It is conflicting we know for a fact that burned people lost their accounts but we don't know if they survived or not. Flashback could be data storm specific. it is hard to say. Yu gioh does have some permanent deaths, bruno, the goodwins, roger, ... .
3) Absolutely. I mean the 2500atk monster hasn't appeared yet.
4) I kind of liked this kind of start but I get the feeling world crisises are a given anyway just wait a few seasons. Give the slice of life while players get used to the characters and new mechanics. The episodes are filled I must admit, which is both a good and bad thing. The only problem I have with the slice of life in this spin-off is that yusaku is kinda detached and uniterested and wouldn't really fit with the slice of life setting.
For female protagonist let them first get a female main character written correctly. I have great hopes for Aoi Zaizen. We still haven't that done right. Also why a tomboy?